JP5000021B1 - Injection stretch blow bottle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection stretch blow bottle made from a polypropylene resin composition which has a desired transparency for a comparatively thick wall. <P>SOLUTION: The injection stretch blow bottle consists of the polypropylene resin composition and has a wall thickness of 0.85-1.6 mm at its trunk section, a ratio of haze value to the wall thickness (hereafter called a normalized haze value) of less than 5.0 %/mm at the trunk section and the haze value of 6.0% or less; wherein the resin component of the polypropylene resin composition is an isotactic polypropylene and/or a propylene-olefin copolymer. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to an injection stretch blow bottle, and more particularly, to a highly transparent injection stretch blow bottle made of a polypropylene resin composition.

  Various types of containers for storing easily leaking substances such as liquids and granular materials are known, and among them, resin containers are frequently used from the viewpoint of moldability and low cost. For liquid products etc., the shape of the bottle with a transparent body is used for the purpose of confirming the presence / absence, color, etc. of the contents from the outside at the time of purchase, and for the purpose of confirming the remaining amount, discoloration, quality change, etc. when the contents are used. A container (hereinafter referred to as a transparent bottle) is used. In particular, transparent bottles for storing cosmetics, beverages, etc. are required not only to make the contents clear and beautiful, but also to have a beautiful appearance and cleanliness of the container itself. For this reason, it is important that the transparent bottle not only has high transparency, but also has a uniform transparency without unevenness in transparency.

  A glass bottle is known as a beautiful and highly transparent bottle, but the glass bottle is heavy and easily damaged. Recently, plastic transparent bottles that are light and hard to break are often used instead of glass bottles. In particular, a transparent bottle (hereinafter sometimes abbreviated as PET bottle) made of polyethylene terephthalate resin (hereinafter sometimes abbreviated as PET resin) is excellent in transparency, homogeneous and strong, It is used for beverage bottles and cosmetic bottles.

  PET bottles have high transparency and can have a haze value of 6% or less, which is an index of transparency, even when the thickness is relatively thick, about 0.7 to 1.0 mm. Usually, if the PET bottle has a wall thickness of 0.7 mm or more, it is possible to obtain a buckling strength of 100 N or more in a 200 ml size bottle without providing a rib for reinforcing rigidity or designing a special shape. it can. If a buckling strength of 100 N can be obtained, there is almost no risk of buckling due to pressure during stacking or transportation even during storage or distribution.

  Recently, it has been proposed to use a transparent bottle using a polypropylene resin (hereinafter sometimes abbreviated as PP resin) instead of a PET bottle. Polypropylene resins are cheaper than PET resins, have superior solvent resistance, and are considered to be relatively easy to mass-produce from biomass materials in the near future.

  As long as the transparent bottle made of resin is a transparent bottle having a thickness of 2.0 mm or less, it can be formed by injection stretch blow molding regardless of whether it is a PET bottle or a transparent bottle made of PP resin (hereinafter referred to as PP bottle). Often manufactured. However, PP bottles produced by injection stretch blow molding generally tend to have poor transparency and transparency uniformity compared to PET bottles. Therefore, it is expected to provide a homogeneous transparent bottle with high transparency, such as a haze value of 6.0% or less, particularly 5.0% or less, from PP resin.

  In general, transparent bottles tend to have low transparency corresponding to an increase in wall thickness. Among transparent bottles made of PP resin having high transparency, transparent bottles having relatively high transparency corresponding to wall thickness and As a manufacturing method, the inventions described in Patent Documents 1 to 5 are known.

  Patent Document 1 discloses a stretch blow molded container having a wall thickness of 0.4 mm and a haze value of 1.2 to 2.0%. This stretch blow molded container uses a polypropylene resin composition containing a propylene ethylene random copolymer having specific physical properties using a metallocene catalyst.

  Patent Document 2 discloses a stretch blow molded container having a body thickness of 0.5 mm and a haze value of 1.9%. As the resin composition of the stretch blow molded container, transparency is improved by molding using a propylene ethylene random copolymer having specific physical properties as a resin component.

  Patent Document 3 discloses a stretch blow molded container having a body thickness of 0.561 mm and a haze value of 2.27% (see Example 7). In this stretch blow molded container, transparency is improved by using a polypropylene-based resin composition in which MI of an ethylene-propylene random copolymer system is specified. However, this stretch blow molded container has a large variation in wall thickness, with a maximum wall thickness of 0.0820 mm and a minimum wall thickness of 0.0366 mm (Table 3, Example 7).

  Patent Document 4 discloses a stretch blow molded container having a body thickness of 0.8 mm and a haze value of 2.0%. As a resin composition of this stretch blow molded container, 87.5% of a propylene-ethylene random copolymer having a specific physical property range as a resin component and 12.5% of a propylene homopolymer are molded. We are trying to improve transparency.

  Patent Document 5 discloses a stretch blow molded container having a body thickness of 0.8 mm and a haze value of 2.0%. As the resin composition of this stretch blow molded container, transparency is improved by molding using a resin composition of a propylene-ethylene random copolymer system having a specific physical property range. However, if the resin composition used here is a molded product having a thickness of 2 mm, the haze value of 12 to 20% and the transparency deteriorates rapidly (see Examples 1 to 8), and the bottle has a thickness exceeding 0.8 mm. It is unclear whether excellent transparency with a haze value of 6% or less can be exhibited.

  There is hardly any invention of PP bottles by stretch blow molding, which is a transparent bottle using a polypropylene resin having a wall thickness exceeding 0.8 mm and has a high transparency with a haze value of 6.0% or less. Patent Document 6 discloses a hollow molded container having a body thickness of 1 mm and a haze value of 5.2%. As the resin composition of this hollow molded container, transparency is improved by molding using a resin composition of a propylene-ethylene random copolymer system.

  As described above, it has been difficult to produce a transparent bottle having a wall thickness exceeding 0.8 mm and a haze value of 5.0% or less by blow molding, particularly injection stretch blow molding, from a polypropylene resin. In particular, since it is difficult to improve the transparency with the thickness, when the thickness exceeds 1 mm, it has been difficult to produce a transparent bottle with excellent transparency having a haze value of 6.0% or less.

  Although not directly applicable to an injection stretch blow molded bottle, the transparency of a test piece having a wall thickness of 1 mm or more prepared by injection molding for measuring a haze value from a polypropylene resin composition is measured. Since it is an injection-molded test piece, it cannot be directly compared with a transparent bottle by injection stretch blow molding, but as an example of a polypropylene resin composition having high transparency, for example, data disclosed in Patent Documents 7 and 8 is there.

  Patent Document 7 discloses an injection molded test piece having a thickness of 1.0 mm and a haze value of 5.0%. This injection-molded test piece uses a polypropylene resin composition using a propylene ethylene random copolymer having specific physical properties using a metallocene catalyst.

  Patent Document 8 discloses an injection molded test piece having a thickness of 2.0 mm and a haze value of 2.0%. This injection-molded test piece uses a polypropylene resin composition containing a total of 80 to 90% of a syndiotactic polypropylene resin and a syndiotactic propylene-ethylene copolymer. Note that syndiotactic polypropylene resins have not been established as industrial products, and are different from normal industrial products such as isotactic polypropylene resins and propylene copolymers containing olefins other than propylene. It is considered to be a resin with different properties.

JP 2006-307122 A Japanese Patent Publication No. 6-39554 Special table 2008-509862 gazette JP 2002-179860 A Special reissue 2008/032735 Japanese Patent Laid-Open No. 10-053676 JP 2009-209342 A JP 2005-340443 A

  As shown in the above Patent Documents 1 to 6, in the case of a transparent bottle, particularly a transparent bottle manufactured by injection stretch blow molding (referred to as an injection stretch blow molding bottle) from a polypropylene-based resin, the wall thickness is 0.8 mm or less. As a thin transparent bottle, a transparent bottle having a haze value of about 2.0% and excellent transparency is known. However, there is a relative relationship between the wall thickness and the haze value, and the haze value tends to increase as the wall thickness increases. In particular, as seen in Cited Document 5, when the thickness exceeds 0.8 mm, the haze value rises rapidly, and those having a haze value of 6% or less, or 5% or less, which are preferable as a resin-made transparent bottle, are known. Absent.

  If a test piece is made from polypropylene resin by injection molding for haze value measurement, the haze value of the test piece may be 6% or less, but injection stretch blow molding that can mass-produce transparent bottles at low cost. It cannot be applied to the product as it is.

  The thickness and haze value of transparent bottles manufactured from polypropylene-based resin by injection stretch blow molding are likely to vary depending on their positions even in the same body part. For example, in the case of the transparent bottle described in Document 3, the minimum side wall thickness is 44.6% of the maximum side wall thickness. Moreover, although specific numerical values are not described in Document 1, in measuring the haze value of a transparent bottle, the thickness and haze value of a plurality of samples are measured in consideration of the variation, and the haze value is obtained as an average value thereof. Represents. According to the study by the present inventors, in the transparent bottle manufactured by the conventional injection stretch blow molding method, the transparency variation exceeding 50% was observed depending on the measurement position even in the body portion of the same transparent bottle.

  According to the study by the present inventors, PP bottles produced by a conventional production method (injection stretch blow molding method) are not only inferior in transparency to PET bottles, but also generally have a thick wall in the body portion requiring transparency. It was also found that unevenness (variation) is likely to occur in the transparency. The occurrence of unevenness in the transparency of the body part may cause not only deterioration of the appearance characteristics of the bottle but also misidentification of the amount, color, and transparency of the contents. In some cases, quality may be uneven, such as the strength of the bottle, which may reduce compression resistance. For this reason, it is an important element as a transparent bottle to make a container without unevenness in transparency. In addition, the PP bottle with a thicker wall not only has a lower transparency of the body part, but also has a tendency to have a larger variation in transparency, and needs to be evaluated as a relative relationship with the wall thickness.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an injection stretch blow bottle having a relatively thick wall and excellent transparency using a polypropylene resin composition as a raw material.

  The present invention is an injection stretch blow bottle made of a polypropylene resin composition, wherein the resin component of the polypropylene resin composition is isotactic polypropylene and / or a propylene-olefin copolymer, 0.85 to 1.6 mm, the ratio of the haze value to the wall thickness of the trunk (hereinafter referred to as normalized haze value) is less than 5.0% / mm, and the haze value is 6.0%. An injection stretch blow bottle characterized by:

  Preferably, the present invention is characterized in that the deviation of the normalized haze value at each location relative to the average value of the normalized haze values at any 3 locations in the barrel is 1.0% / mm or less. It is a blow bottle.

  In a preferred embodiment of the present invention, the ratio of haze values (smaller value / larger value) at any two locations of the body is 0.5 or more.

  A preferable present invention is the injection stretch blow bottle, wherein the propylene-olefin copolymer contains ethylene as an olefin.

  In a preferred aspect of the present invention, the body is a substantially cylindrical shape, a substantially elliptical column, a polygonal column having a substantially polygonal section, or a polygonal column having a substantially polygonal section and a smooth corner. It is the said injection stretch blow bottle characterized by these.

  In a preferred aspect of the present invention, the resin component of the polypropylene resin composition is the injection stretch blow bottle, wherein the resin component is produced mainly from a biomass raw material.

  According to the present invention, it is possible to provide an injection stretch blow bottle having a relatively thick wall and excellent transparency using a polypropylene resin composition as a raw material.

Drawing 1 is a front view (A), a side view (B), and a top view (C) of an injection stretch blow bottle concerning an embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining an injection molding machine in cold parison type injection stretch blow molding, which is an example of a method for producing an injection stretch blow bottle according to an embodiment of the present invention. 3 is a detailed sectional view of the vicinity of the fixed die plate 26 of the injection molding machine in FIG. FIG. 4 is an explanatory diagram of a process of creating a blow bottle from a preform by stretch blow molding in a cold parison type injection stretch blow molding that is an example of a method of manufacturing an injection stretch blow bottle according to an embodiment of the present invention. is there. FIG. 5 is an explanatory diagram of a temperature profile of the molding resin in the cold parison type injection stretch blow molding. FIG. 6 is a graph showing the relationship between the crystallization and the melting temperature and the calorific value of a polypropylene-based resin that is a raw material of the injection stretch blow bottle according to the embodiment of the present invention, by differential scanning calorimetry (DSC) analysis. FIG. 7 is an explanatory diagram of a method for manufacturing an injection stretch blow bottle according to an embodiment of the present invention by hot parison type injection stretch blow molding. FIG. 8 is an explanatory view of a temperature profile of a molding resin in hot parison type injection stretch blow molding. FIG. 9 is a view showing the relationship of the haze value with respect to the thickness of the injection stretch blow bottle shown in the examples and comparative examples. FIG. 10 is a diagram showing the relationship between the normalized haze value and the hot runner outlet temperature of the injection stretch blow bottle injection molding machine shown in the examples and comparative examples.

  The present invention relates to an injection stretch blow bottle with high transparency using a polypropylene resin composition. The polypropylene resin composition (also referred to as PP resin composition), which is a raw material of the injection stretch blow bottle of the present invention, includes isotactic polypropylene, copolymer polypropylene, or isotactic polypropylene and copolymer polypropylene as resin components. Is used. The injection stretch blow bottle of the present invention has a barrel thickness of 0.85 mm to 1.6 mm, a barrel haze value of 6.0% or less, and a haze value relative to the barrel thickness. The ratio (hereinafter, the ratio of the haze value to the thickness of the body portion is referred to as a normalized haze value) is less than 5.0% / mm. In a preferred embodiment of the present invention, the deviation from the average value of the normalized haze values at any three locations of the trunk is 1.0% / mm or less. In a preferred injection stretch blow bottle of the present invention, the ratio of the haze values at any two locations in the body (calculated as the ratio of the small value to the large value) is 0.5 or more.

  Specific embodiments of the injection stretch blow bottle of the present invention will be described. The injection stretch blow bottle according to the embodiment of the present invention is manufactured by injection stretch blow molding, preferably cold parison type injection stretch blow molding. Injection stretch blow molding can mass-produce relatively thin, high-strength, homogeneous plastic bottles with a thickness of 2 mm or less, and the production cost for mass production is also low. A bottle is a container having an opening having a constriction on a body having a substantially constant cross section, such as a bottle, a bowl, a bottle, etc. Any shape such as an ellipse, a polygon, or a polygon with smooth corners may be used. Moreover, shapes, such as a rib, embossing, an unevenness | corrugation, may be attached | subjected to the trunk | drum etc.

(Injection stretch blow bottle)
The injection stretch blow bottle of the present invention (hereinafter, the injection stretch blow bottle may be referred to as a transparent bottle) will be described with reference to specific embodiments. FIG. 1 shows a transparent bottle according to an embodiment of the present invention. The transparent bottle of the present embodiment is a polypropylene transparent bottle (also referred to as a PP bottle) 10 having a substantially elliptic columnar body manufactured by cold parison type injection stretch blow molding. 1A is a front view of the transparent bottle 10, FIG. 1B is a side view of the transparent bottle 10, and FIG. 1C is a plan view of the transparent bottle 10. The transparent bottle 10 shown in FIG. 1 is effective as a container or the like that is used by inserting a liquid material such as cosmetics or beverages. The shape of the transparent bottle 10 is generally configured such that the body 11, the neck 12, the shoulder 13, and the bottom 14 are integrally formed. The neck portion 12 is formed with a thread groove, the body portion 11 is formed with a gentle recess 17, the bottom portion 14 is slightly recessed inward, the body portion 11 and the corner portion 15 of the shoulder portion 13, and the body portion 11. And the corner | angular part 16 of the bottom part 14 is each shape | molded by the curved surface. The transparent bottle of this embodiment has an internal volume of about 200 ml, a weight of about 27 g, and an average wall thickness of 0.85 to 1.6 mm.

  The transparent bottle 10 of the present embodiment is not limited to the above shape, and may have another shape. The body of the transparent bottle 10 may have a substantially cylindrical shape, a substantially elliptical column, a polygonal column having a substantially polygonal cross section, or a polygonal column having a substantially polygonal corner having a smooth corner. preferable. In addition, strength reinforcing or decorative ribs, concavo-convex patterns, embossed patterns, corrugated patterns, sawtooth patterns, and the like may be formed on the bottle-shaped body.

  In the present embodiment (assuming a 200 ml capacity bottle), the measurement region when measuring the wall thickness and haze value in the trunk portion 11 is formed below the corner portion 15 which is the boundary between the shoulder portion 13 and the trunk portion 11. Due to the molding, the portion below the portion where the large disturbance of the resin thickness due to the resin disappears, usually at a distance of about 5 mm or more from the shoulder portion 13 and on the corner portion 16 which is the boundary with the body portion 11 of the bottom portion 14 A portion above the portion where the large change in the resin thickness or the like has disappeared, usually a portion separated from the bottom 14 by about 5 mm or more is preferable.

-Thickness of trunk | drum The transparent bottle in this embodiment represents thickness of a trunk | drum (henceforth only "thickness", unless otherwise indicated, "thickness (mm) of the trunk | drum of a transparent bottle)." However, the lower limit is 0.85 mm or more, preferably 0.9 mm or more, particularly preferably more than 1.0 mm, and the upper limit is 1.6 mm or less, preferably 1.5 mm or less, particularly preferably 1.4 mm. It is as follows. If the thickness of the body part is thinner than the above lower limit, depending on the shape of the transparent bottle, the desired strength may not be maintained, and buckling is likely to occur, or damage due to impact, protrusions, or the like is likely to occur. Also, if the thickness of the barrel becomes thicker than the above upper limit, the amount of resin used will increase, the container weight will increase, the merit of transport and handling will be smaller than PET bottles, etc., and the manufacturing cost will increase. Highly transparent containers are difficult to manufacture. In addition, the thickness of the said trunk | drum should just be the average value of those measured values, when measuring the several location of one transparent bottle.

-Haze value of barrel part Generally, the performance required as a transparent bottle with high transparency is such that the transparency of the barrel part is 6.0% or less, preferably 5.0% or less, particularly preferably 4.5% in terms of haze value. % Or less, more preferably 4.0% or less, 3.0% or less, 2.5% or less, or less than 2.0%. The haze value of the body portion of the transparent bottle in the present embodiment (hereinafter simply referred to as “haze value” means “the haze value (%) of the body portion of the transparent bottle” unless otherwise specified)). The transparency is equivalent to or higher than the haze value of a transparent bottle made of PET having a wall thickness of about 0.8 to 1.5 mm. In addition, what is necessary is just to represent the haze value of the trunk | drum of a transparent bottle by the average value of those measured values, when the several location of one transparent bottle is measured.

  Conventionally, many transparent bottles made of polypropylene have a thickness of 0.05 to 0.8 mm. As shown in Patent Documents 1 to 6, such a thin bottle has been manufactured with a high transparency such as a haze value of about 2 to 5%. However, there are few examples of highly transparent bottles with a wall thickness of more than 0.8 mm, especially 0.85 mm or more and a haze value of 6.0% or less. A transparent bottle by injection stretch blow molding of 6.0% or less has not been known. According to the investigation by the present inventors, the transparent container having a wall thickness exceeding 0.8 mm and a haze value of 6.0% or less was the only one disclosed in Patent Document 6. However, this transparent container is not an injection stretch blow bottle but a hollow molded container.

  The lower limit of the haze value is preferably smaller, but considering a realistic production method, it is 1.0%, preferably 1.4%, particularly preferably about 1.8%. In the present embodiment, a transparent bottle having a haze value (average value of three measured values) of 1.8 to 5.3% can be provided. Based on the results of Examples described later, it is considered that transparent bottles having a haze value of 1.0% and at least 1.4% can be mass-produced by selecting production conditions.

Normalized haze value (haze value / wall thickness)
Conceptually, the haze value is a light scattering characteristic (referred to as “surface haze value”) of the surface of a sheet-like molded body, which is a test piece cut out from a transparent bottle, and a light scattering characteristic (“internal haze value”) inside the test piece. It is expressed as the sum of In this paragraph, the normal haze value is referred to as “total haze value” in order to distinguish it from “surface haze value” and “internal haze value”. According to the study of the present inventors, in the case of a transparent bottle molded under the same molding conditions from the same PP resin composition by the injection stretch blow molding method of the present inventors, the wall thickness is 0.85 to 1.6 mm. In the range of the above, in an injection stretch blow molded bottle having a high transparency such as a total haze value of 6.0% or less, light scattering on the surface is hardly suppressed, and the “surface haze value” is close to 0%. It was found that the “value” mostly depends on the “internal haze value”, which is the light scattering property inside the molded body. Then, if the sample for measuring the haze value is a homogeneous molded body (injection stretch blow molded body uniformly molded by the same molding method), there is a proportional relationship between the wall thickness and the haze value, and the haze value is It makes sense to normalize by thickness (convert to haze value per unit thickness). Therefore, the present inventors use the normalized haze value obtained by normalizing the haze value with the thickness (the haze value (%) at a predetermined measurement location / the thickness (mm) at the same measurement location). The physical properties of transparent bottles were arranged.

  When there is a proportional relationship between the thickness and the haze value of a molded product obtained by molding a transparent bottle from the same PP resin composition under similar injection stretch blow molding conditions, for example, when the thickness is 1.3 mm, the haze value is 3 If a 25% transparent bottle (normalized haze value = 3.25% / 1.3 mm = 2.5% / mm) can be produced, the haze value is about 2 when the thickness is 1.0 mm by the same production method. When the thickness is 1.5% and the wall thickness is 1.5 mm, a transparent bottle having a haze value of about 3.75% can be produced. If the manufacturing method of the transparent bottle demonstrated later is applied, as shown in the below-mentioned Example (refer Table 1 etc.), the haze value of the transparent bottle from which only the thickness produced from the same resin on the same molding conditions differs only in the above-mentioned It almost supports the assumption.

  The transparent bottle of the present invention has a normalized haze value expressed as a haze value normalized by the thickness of the trunk (haze value / thickness), less than 5.0% / mm, preferably 4.5% / mm or less, 4.0% / mm or less, more preferably 3.0% / mm or less, and even more preferably 2.2% / mm or less. The transparent bottle of the present invention is a transparent bottle with suitable transparency as long as the wall thickness is 0.85 mm or more and 1.6 mm or less and the normalized haze value is within the above limit value. The haze value can be easily manufactured even with a transparent bottle of 1.0% or less if the wall thickness is very thin, but 1.0% in the case of a transparent bottle having a relatively large wall thickness, for example, about 1.0 mm. It is difficult to make it less than. Therefore, it is conceivable to use a normalized haze value instead of a mere absolute value of the haze value for setting the lower limit value of the haze value. The lower limit value of the normalized haze value is preferably smaller, but 1.0% / mm, preferably 1.3% / mm, particularly preferably 1. If it is about 4% / mm, it can manufacture.

-Variation in normalized haze value Generally, in a transparent bottle, variation in transparency depending on location is conspicuous, and if there is variation in transparency, the commercial value decreases. This tendency is particularly strong in transparent bottles with high transparency. On the other hand, transparent bottles with a wall thickness of 2.0 mm or less are often manufactured by injection stretch blow molding. In injection stretch blow molding, resin is stretched in the container manufacturing process like a cold parison type stretch blow molding method. The homogeneity of the state and temperature profile during molding may not be sufficient. If it does so, it will become easy to produce the variation in the transparency by the measurement position of a transparent bottle.

  The haze value of the transparent bottle is likely to change in relation to the wall thickness, as described above, in addition to the variation in transparency. Therefore, it is preferable to use the deviation of the normalized haze value in order to evaluate the variation in the transparency of the transparent bottle while removing the influence of the wall thickness. The deviation of the normalized haze value of the transparent bottle is the deviation of the normalized haze value of each location relative to the average value of the normalized haze values of two or more locations of the target transparent bottle ((average value of normalized haze values) -(Normalized haze value of each part)). In the embodiment of the present application, the deviation of the normalized haze value is determined by measuring the normalized haze value at any three locations of the transparent bottle, obtaining an average value thereof, and calculating the normalized haze value at each of the three locations relative to this average value. Expressed in absolute value of difference.

  The tolerance of the deviation of the normalized haze value of the transparent bottle according to this embodiment is 1.0% / mm or less, preferably 0.8 or less. When the deviation of the normalized haze value of the transparent bottle exceeds the allowable value and becomes 1.1% / mm or more, variation in transparency and non-uniformity in transmitted light are recognized, and the color and transparency of the contents are accurately observed. As a transparent bottle, the product value is reduced.

  In addition, as for the transparent bottle made from conventional PP resin, the variation in the ratio of the thickness and the haze value due to the position of the body portion of one transparent bottle is unknown because there is no literature describing this, but in the examples described later As shown in Table 1, in the measurement results of deviations of the normalized haze values at three locations for a transparent bottle made of PP that is considered to be an excellent commercial transparency with little variation in transparency, the normalized haze value is The average value was 5.5%, and the deviation of the normalized haze value was 0.33% / mm, 0.62% / mm, and 0.96% / mm. In this example, the average normalized haze value is 5.0% or more, which is different from the transparent bottle according to the present invention.

  In addition, the transparent bottle according to the present invention has a tolerance of variation in normalized haze value that is the difference between the normalized haze values at any two locations on the body of one transparent bottle (larger haze value minus smaller one). Haze value). In the transparent bottle according to the present invention, the difference between the normalized haze values at any two positions of the body portion is 1.6% / mm or less, preferably 1.4% / mm or less, particularly preferably 1.0% / mm. It is preferable that it is mm or less.

-Variation in haze value ratio The variation in transparency of a transparent bottle can also be evaluated as variation in the haze value of a transparent bottle. The variation in the haze value of the transparent bottle is expressed as the ratio of the haze values at any two locations on the body of one transparent bottle. The ratio of the haze values at any two locations in the body of one transparent bottle (for convenience, expressed as a small measurement value / a large measurement value) is preferably 0.5 or more, particularly preferably 0.6 or more. That is, of the haze values at any two locations on the body, where A% is a large measured value and B% is a small measured value, B / A is 0.5 or more, in other words, any two locations on the body. The haze value ratio is preferably in the range of 1: 2 to 2: 1.

-Buckling strength The transparent bottle of this embodiment represents the buckling strength in the vertical direction of the trunk (hereinafter referred to as "buckling strength" unless otherwise specified). .) Is 100N or more. The buckling strength is the resistance when the containers are stacked or compressed from the upper part. Usually, if it is 100N or more, special care is not required for transportation, storage and handling during use. ing. Normally, the buckling strength of the transparent bottle is the smallest at the body and is often buckled first. Therefore, in the buckling strength measurement, only the body may be taken out. The buckling strength may be measured by compressing itself in the vertical direction. In addition, the buckling strength measurement has a capacity of 100 to 2000 l, (equivalent diameter of the body part): (height of the body part) is 1: 0.5 to 1: 5, and the shape of the body part is substantially What is necessary is just to measure in a cylindrical, elliptical column shape, or a polygonal column-shaped transparent bottle with a polygonal cross section.

(Polypropylene resin composition)
The polypropylene-based resin composition in the present invention is a concept including a polypropylene-based resin composition composed only of a polypropylene-based resin as a resin component, and a polypropylene-based resin composition mainly composed of a polypropylene-based resin and containing a small amount of additives.

  As is well known, polypropylene resins include homopolymers (polymers composed only of polypropylene alone) and copolymers (copolymers of polypropylene and other monomers). Homopolymers include isotactic, syndiotactic, and atactic polymers. In the present invention, it is preferable to use an isotactic polymer. These classifications are quantitatively relative, and are polypropylene polymers of the present invention as long as they are isotactic polymers having an isotacticity that is generally considered to be an isotactic polymer. It is suitable as.

  Copolymers include random copolymers, block copolymers, alternating copolymers, and the like. The copolymer is preferably a copolymer containing an olefin-based monomer other than propylene, and in particular, a propylene ethylene random copolymer and a random copolymer having a structure in which a small amount of ethylene and / or α-olefin is randomly incorporated in a propylene chain are preferable. The polypropylene resin may be a resin composition obtained by mixing a plurality of these homopolymers and copolymers.

  The polypropylene resin used in the transparent bottle of this embodiment is preferably one that has been polymerized with a Ziegler-Natta catalyst. Polypropylene resin polymerized with a Ziegler-Natta catalyst is different in orientation characteristics from those polymerized with a metallocene catalyst and the mechanism of crystal formation is different, so the buckling strength is high and the haze value is small. It is considered that a transparent bottle with little variation is obtained. A polypropylene resin using a Ziegler-Natta catalyst or a metallocene catalyst is likely to be an isotactic homopolymer or a random copolymer close thereto because propylene isotacticity is improved.

  The transparent bottle of the present embodiment is preferably substantially isotactic polypropylene resin as a homopolymer. Although there is literature that syndiotactic polypropylene resin is suitable for improving the transparency, there is a problem in raw material resin production when the transparent bottle is industrially produced, and the strength is not sufficient. In order to increase the strength, it is necessary to increase the wall thickness, but not only the transparent bottle becomes heavier, but the amount of resin used increases and the cost tends to increase.

  It is preferable that the polypropylene resin used in the transparent bottle of the present invention is produced mainly from biomass raw materials. In the future, it is considered that a polypropylene resin produced from a plant material mainly composed of a biomass material having a small environmental load will be available at a low cost. For example, if a corn starch is used to produce propylene, ethylene or the like via an alcohol such as propanol or ethanol and then polymerized, a 100% plant-derived polypropylene resin can be produced.

(Additive)
In the transparent bottle of the present invention, if necessary, various additives such as an antioxidant, an ultraviolet absorber, a flame retardant, and a nucleating agent are added to the raw material polypropylene resin to adjust the performance of the resin. Can do. On the other hand, since polypropylene resins are excellent in solvent resistance, chemical resistance, etc., it is preferable to use additives in consideration of not lowering these characteristics by the addition of additives.

[Method for producing transparent bottle of the present invention]
The transparent bottle of the present invention can be produced by injection stretch blow molding. Injection stretch blow molding includes a cold parison type and a hot parison type. First, as a preferred embodiment, a method for producing a cold parison type transparent bottle will be specifically described with reference to the drawings.

(Cold Parison type injection stretch blow molding)
(Preform molding)
The cold parison type injection stretch blow molding, which is a preferred embodiment of the method for producing a transparent bottle of the present invention, will be described. FIG. 2 is a schematic diagram for explaining cold parison type injection stretch blow molding, which is an embodiment of the method for producing a transparent bottle according to the present invention.

  In order to manufacture the transparent bottle 10 by cold parison type injection stretch blow molding, first, an injection molding machine 20 as shown in FIG. 2 is prepared. The injection molding machine 20 includes an injection mold 25 for forming a preform (also referred to as a parison).

  In FIG. 2, the injection molding machine 20 has an extrusion screw 23 inside a heating cylinder 22. Resin pellets 30 made of a propylene-based resin composition are loaded into a hopper 24 installed at the top of the heating cylinder 22, the resin pellets 30 are introduced into the heating cylinder 22 by the rotation of the extrusion screw 23, and are heated and kneaded by the heating cylinder 22. Then, the molten resin 31 is transferred to the resin outlet (injection mold 25 side) of the heating cylinder 22. The injection mold 25 is sandwiched between a fixed die plate 26 fixed to the injection molding machine main body 21 and a movable die plate 27 which is paired with the fixed die plate 26 and is movable. Is installed.

  As shown in FIG. 3, the fixed die plate 26 is provided with a hot runner 28 for connecting the resin outlet of the heating cylinder 22 and the resin inlet of the injection mold 25. The molten resin 31 in the heating cylinder 22 is injected into the hot runner 58, transferred to the injection molding die 25 side as a molten resin 32, and into the cavity (internal space) 35 of the injection molding die 25. It is injected. This hot runner 28 is generally called a runner section (or runner), and an injection molding machine of the type that forcibly heats or keeps the molten resin 32 in the runner section by a heater 29 is a hot runner type, and heating or keeping heat by the heater 29. An injection molding machine equipped with a runner section that is not used is called a cold runner type to distinguish. In the transparent bottle manufacturing method of the present embodiment, an injection molding machine including a hot runner type runner (hot runner 28) is used.

  The molten resin 31 injected from the resin outlet of the heating cylinder 22 is heated by the heater 29 in the resin passage of the hot runner 28 and becomes a molten resin 32 heated to a temperature equal to or higher than the temperature of the molten resin 31 to form an injection mold. It is introduced into a cavity 35 in the shape of 25 preforms (parisons) 40. In this way, the entire inside of the cavity 35 is filled with the molten resin 32 and becomes the shape of the preform 40 to become the resin 33.

  The injection mold 25 is cooled by circulating water or the like of about 0 to 35 ° C., and the resin 33 in the cavity 35 molded into the shape of the preform 40 is rapidly cooled and solidified, and the hot preform 40 is cooled. It becomes. The surface of the hot preform 40 is cooled and solidified to maintain the shape of the preform 40, but the inside is not sufficiently cooled, and the resin inside is completely solidified and crystallized. There are many cases of no state. In the hot parison type injection stretch pro-molding in the present embodiment, the temperature of the hot preform 40 (the surface temperature of the preform) is preferably lower than the crystallization temperature of the used polypropylene resin, specifically, It is preferably 110 ° C. or lower, particularly 100 ° C. or lower.

  In the manufacturing method of the transparent bottle of this embodiment, the temperature of the molten resin 32 in the hot runner 28 is heated to 180 to 300 ° C., preferably 220 to 280 ° C., more preferably 220 to 260 ° C. It is injected into the cavity 35 of the mold 25. The temperature of the resin introduced into the cavity 35 of the injection mold 25 is strictly controlled by the heater 29 in the runner portion. In molding of a polypropylene resin by injection stretch blow molding of the conventional hot runner type (also in the cold runner type), the molten resin 32 that passes through the runner portion is raised rather than the temperature of the molten resin 32 that passes through the runner portion. It was only heated for keeping warm enough to prevent a decrease in temperature. For this reason, the temperature of the molten resin 32 in the runner portion was not strictly controlled even with the heater 29.

  In the production example of the transparent bottle of the present embodiment, it is preferable that the preform molding temperature, that is, the temperature of the molten resin 32 passing through the runner portion is 180 to 300 ° C. However, the temperature of the molten resin 31 at the inlet of the hot runner 28, that is, the temperature of the molten resin 31 in the heating cylinder 22 is preferably lower than the temperature of the molten resin 32 at the outlet of the hot runner 28. Usually, when a polypropylene resin is heated in a heating cylinder 22 of an injection molding machine at 200 ° C. or more for a long time, thermal decomposition of the molten resin 31 occurs due to temperature unevenness in the heating cylinder 22 or shearing force by the screw 23. The molecular weight is likely to decrease, which is not preferable. Further, conventionally, also from the viewpoint of energy saving, the resin temperature in the heating cylinder 22 (the set resin temperature of the heating cylinder 22) should be as low as possible within a moldable range, for example, less than 220 ° C. or 200 ° C. or less. Was preferred. In this case, the actual resin temperature of the runner part is often lower than the resin temperature of the heating cylinder 22 because the heating amount of the hot runner is small even in the hot runner. Conventionally, with a normal polypropylene resin, if the resin temperature of the heating cylinder 22 is less than 200 ° C., injection molding can be performed without any problem. However, it is considered that there was no problem because a transparent bottle having high transparency as intended in the present application was not required.

  However, in this application, since the resin temperature injected into the injection mold 25 is desired to be relatively high, the resin 31 in the heating cylinder 22 is set to 200 to 280 ° C., preferably close to 220 to 280 ° C. The temperature is introduced into the hot runner 28. Further, the molten resin 32 is heated by the heater 29 disposed on the hot runner 28, and the hot runner 28 (strictly, the resin outlet portion of the hot runner 28 to the injection mold 25) is at or above the temperature of the molten resin 31. 200-280 ° C., preferably 220-280 ° C., is introduced into the injection mold 25. In the present embodiment, the temperature range is appropriately selected depending on the properties of the resin used, and the resin temperature 31 in the heating cylinder 22 is increased within a range in which decomposition and molecular weight reduction do not occur. A transparent bottle having excellent transparency can be obtained. However, when the temperature of the molten resin 31 is 300 ° C. or higher, the haze value of the transparent container and the variation in the haze value tend to increase.

  Since the molten resin 32 introduced into the injection mold 25 has a temperature of 180 to 300 ° C., crystals in the molten resin completely disappear and are in a homogeneous molten state. When this high-temperature molten resin is introduced into the cavity 35 of the injection mold 25 cooled to about 35 to 10 ° C. by cooling water, the molten resin 33 is solidified in the cavity while being rapidly cooled. start. The molten resin 33 is further cooled in the cavity for a predetermined time, and then released from the injection mold 25 as a hot preform when the surface is solidified and the shape of the preform can be maintained as a whole. The In the case of cold parison type injection stretch blow molding, the inside of the preform is usually allowed to cool to room temperature and stored as a preform 40. The transparent bottle 10 is manufactured by heating and preforming the preform 40 stored at the room temperature again at a necessary place when necessary. As will be described in detail later, in the case of hot parison type injection stretch blow molding, a hot preform 40 that can maintain its shape at the time of mold release is immediately transferred to the next stretch blow molding step.

  In the manufacturing example of the transparent bottle of the present embodiment, the hot preform 40 taken out from the injection mold 25 is crystallized up to the internal resin until it reaches a temperature at which crystallization does not proceed any further. It is desirable to increase the cooling rate of the preform 40 by performing a forced cooling process instead of allowing it to cool. Actually, it is desirable to forcibly cool the preform 40 until the temperature of the preform 40 becomes 100 ° C. or lower, preferably 80 ° C. or lower, particularly preferably 60 ° C. or lower. The temperature of the preform 40 is measured at the surface temperature. By forcibly cooling the hot preform 40, the resin inside the preform 40 is rapidly cooled at a cooling rate close to the cooling rate in the injection mold 51 to suppress crystal formation itself, It is possible to make fine and small crystals by suppressing the growth. Thereby, the haze value and thickness variation of the transparent bottle after blow molding can be suppressed, and the transparency can also be improved. In addition, as a cooling process, it fully cools until it reaches a predetermined temperature in the injection mold 25, or the hot preform 40 immediately after being taken out from the injection mold 25 is brought into contact with cold water, What is necessary is just to put in a refrigerator etc. or to cool by applying cold air.

(Stretch blow molding)
4A to 4F are schematic cross-sectional views illustrating a cold parison stretch blow molding process. For the stretch blow molding in the present embodiment, a conventional stretch blow molding machine 46 can be used. This will be described with reference to FIG. 4. As described above, the preform 40 is first molded by the injection molding machine 20 having, for example, about 1 to 8 pieces (see FIG. 2). The molded preform 40 is cooled to room temperature and stored. When the transparent bottle 10 is produced from the stored preform 40, as shown in FIG. 4A, a raw material polypropylene resin composition (PP resin) is used by using a heater 45 for the preform 40 at room temperature. The temperature is lower than the melting temperature of (also referred to as)) and is reheated to a predetermined temperature at which the shape of the preform can be maintained for a short time, for example, 110 to 150 ° C., preferably about 115 to 130 ° C. Next, as shown in FIG. 4B, the preform 41 heated to a predetermined temperature and softened is mounted on a blow molding die 47. Here, the portion below the neck of the preform 41 is inserted into the cavity 48 (molding internal space) of the blow molding die 47.

  Subsequently, as shown in FIG. 4C, a stretching rod 49 is inserted from the upper opening of the preform 41, and the soft preform 41 presses the inner bottom downward (toward the bottom of the cavity 48). The preform 42 is stretched (longitudinal stretch). As shown in FIG. 4D, when the inner bottom portion of the longitudinally stretched preform 42 is pressed and stretched to the lower portion (bottom portion) of the cavity 48 and completely stretched in the longitudinal direction to form the preform 43, FIG. ), By blowing air from a small hole provided in the side portion of the stretching rod 49, the preform 43 that has been completely stretched in the longitudinal direction is expanded and stretched laterally (laterally). Direction stretching). The biaxially stretched molded body 44 thus stretched in the longitudinal and lateral directions (biaxial stretching or stretch blow) is in contact with the inner wall of the blow molding die 47 and the transparent bottle 10 along the shape of the cavity 48. Molded into a shape, the inner wall of the blow molding die 47 is deprived of heat and cooled. FIG. 4E shows a state in which the biaxially stretched molded body 44 is in close contact with the entire inner wall of the blow molding die 47 and the shape of the transparent bottle 10 is formed.

  When the biaxially stretched molded body 44 is formed in the cavity 48 of the blow molding die 47 and cooled, the transparent bottle 10 is obtained. As shown in FIG. It is released from. The transparent bottle 10 is manufactured through the above steps.

(Preform cooling temperature)
As a preferred production example of the transparent bottle of the present invention, a preform cooling step will be described. FIG. 5 is a schematic diagram of a resin temperature profile in each step of cold parison type injection stretch blow molding. In each step of preform molding, preform cooling, and bottle molding shown in FIG. 5, the resin temperature follows a temperature course as shown by a solid line with time. Referring to FIG. 5, at the time of preform molding by the injection molding machine 20, first, the resin at room temperature is heated and melted in the heating cylinder 22 of the injection molding machine and becomes close to the molding temperature of the preform. Then, the molten resin 31 heated and melted is further heated by the hot runner 28 to reach a molding temperature t ₁ and is introduced into the injection mold 25. In the manufacturing example of the transparent bottle of the present embodiment, the temperature t _{1 of the} resin heated by the hot runner 28 and inserted into the injection mold 25 is equal to or higher than the resin temperature heated and melted in the heating cylinder 22. And it is preferable to set to 180-300 degreeC.

Next, the molten resin 32 introduced into the cavity 35 of the injection mold 25 is cooled in the injection mold 25 to become a hot resin 33 whose surface is solidified and separated from the injection mold 25. Molded and hot preform 40 is obtained. Resin temperature during the release of the hot preform 40 (the surface temperature of the preform) is t _2. The released hot preform 40 is allowed to cool to room temperature as it is, becomes a room temperature preform 40, and is stored or immediately transferred to a stretch blow process to manufacture the transparent container 10. In FIG. 5 steep listed obliquely lower right position of the temperature t ₂ during release of the hot preform 40 dashed lines, of the preform 40 in the case of forced cooling of the hot preform 40 Indicates the cooling state.

  Here, the crystallization temperature region (crystallization temperature) will be described. The crystallization temperature and the crystal melting temperature of the polypropylene resin (PP resin) that is the raw material of the transparent bottle 10 were analyzed by differential scanning calorimetry (DSC). FIG. 6 shows a molten resin cooling curve and a crystal melting curve by differential scanning calorimetry (DSC) twice each. The upwardly convex curve shown on the upper side of FIG. 6 shows the crystallization temperature profile (molten resin cooling curve) of the molten PP resin. The temperature range in which this high-temperature molten PP resin exhibits a large exotherm with crystallization was 129 ° C. to 111 ° C., and the peak value was 116 ° C. This region is a temperature region called a PP resin crystallization region or a crystal growth region, and is a temperature region in which crystals are produced from the molten PP resin or the produced microcrystals are crystal-grown. When the molten PP resin is at 110 ° C. or lower, crystallization and crystal growth hardly occur, and the portion that has not been crystallized is almost solidified in an amorphous state as it is.

  On the other hand, the melting temperature profile (crystal melting curve) due to heating of the low-temperature resin that is solidified and partially crystallized is shown by a gently downwardly convex curve expressed below the 0 mW line in FIG. It is. As can be seen from the DSC measurement results in FIG. 6, the melting temperature of the resin crystals is relatively broad from around 130 ° C. to around 160 ° C., and the peak value is around 150 ° C. This region is a melting temperature region of the PP resin. When the solidified PP resin is heated to 130 ° C. or higher, the crystallized or solidified portion starts to melt and becomes a molten resin. Thus, it can be seen that PP resin has a difference between the crystallization temperature region (crystal growth region) and the melting temperature region, and the crystallization temperature region is lower than the melting temperature region. It can also be seen that the crystallization temperature region is in a relatively wide temperature range.

In stretch blow molding of a conventional cold parison type, for cooling at room temperature in the preform cooling stage shown in FIG. 5, the hot preform 40 that has just been release is along the solid line from the position of the resin temperature t ₂ And cool slowly. Resin temperature t ₂ during release of the hot preform 40 is preferably lower than the crystallization temperature of the resin used. Since the resin in the cavity 35 of the injection mold 25 is rapidly cooled by the injection mold 25, the resin rapidly changes from a molten state to a solid state. For this reason, the resin in the cavity 35 only stays in the crystallization temperature region for a short time. If it does so, resin will not fully crystallize, but it will solidify, without especially crystal growth. By making such a preform 40, it is considered that a transparent bottle having high transparency and uniform transparency is finally obtained. If injection stretch blow molding of a cold parison type, below the crystallization temperature of the resin temperature t ₂ of the resin during the release of the hot preform 40, for example 110 ° C. or less, preferably is easy to 100 ° C. or less is there.

Incidentally, the preform 40 has a resin temperature t ₂ close to the crystallization temperature of the resin (e.g., about 110 to 100 ° C.) when, since the temperature of the preform 40 is measured at its surface temperature, just after release hot The resin temperature inside the preform 40 may be higher than the crystallization temperature of the resin. When this hot preform 40 is allowed to cool at room temperature, the resin inside the preform 40 is cooled while being higher than the crystallization temperature of the resin, and the resin inside the preform 40 has a crystallization temperature. There is a possibility of staying in the region for a long time and solidifying while crystal growth. Then, as will be described later, there is a possibility that the finally produced transparent bottle is not sufficiently high and uniform transparency can be obtained. For this reason, since the crystallization temperature of polypropylene resin is often about 111 to 130 ° C., the resin temperature t ₂ at the time of releasing the preform 40 is preferably 110 ° C. or less, particularly preferably 100 ° C. or less.

Resin temperature t ₂ is close to the crystallization temperature of the resin used, particularly when higher than the crystallization temperature, it is desirable to immediately forced cooled process the hot preform 40 after release. As a method of forcible cooling treatment, cooling water spraying on the preform 40, charging of the preform 40 into ice water, air cooling to the preform 60, or the like may be used. 5, when the forced cooling process the preform is the temperature profile along the dashed line toward the lower right steeply than the solid line in terms of resin temperature t _2.

Forced cooling process of the preform 40, resin temperature t ₂ is effective even when less than the crystallization temperature of the resin used. As described above, in the hot preform 40, the internal resin temperature may be higher than the resin temperature on the surface, or the crystallization temperature of the resin may vary, and the crystallization temperature of the polypropylene resin is 111. Since there are many cases of about ~ 130 ° C, the hot preform 40 is forcibly cooled in the injection mold 25 or forcibly cooled after the mold release. It is desirable to cool down to a temperature of ℃ or lower, more preferably 80 ℃ or lower.

Next, the preform 40 cooled to room temperature is stretch blow molded by a stretch blow molding apparatus as shown in FIGS. 4 (A) to 4 (F). By the heater 45 of the stretch blow molding machine 46, and heating the resin temperature to stretch blow molding temperature t _3, after the resin temperature has stretch blow molding when it becomes t _3, a cooled transparent bottle 10 product to room temperature.

  Here, the state of crystal generation from the molten resin and the effect when the resin injected into the injection mold 25 is solidified to become the preform 40 will be described. The crystals in the preform 40 are one of the factors that affect the transparency of the container in the production of transparent bottles by stretch blow molding, and that fine crystals are uniformly formed and the amount of crystals is small. However, it is considered to be important for improvement of transparency and uniformity of transparency.

  Of the resin injected into the cavity 35 of the mold 25 for injection molding, the resin introduced into a portion far from the resin inlet of the cavity 35 (resin injected at the beginning of one injection into the cavity 35) Accordingly, the resin introduced into the portion close to the resin inlet (the resin injected at the end of one injection into the cavity 35) has a shorter cooling time in the cavity 35. Further, the resin introduced into the cavity 35 away from the resin inlet flows in the cavity 35 while being mixed with cooling. The crystallization temperature of the polypropylene resin is about 110 to 130 ° C., but crystallization and crystal growth occur when the resin comes into contact with the wall surface of the injection mold 25 and is cooled to the crystallization temperature region. Then, the resin injected into the part of the cavity 35 far from the resin inlet has a longer cooling time by the injection mold 25 and is cooled while being mixed, so that the crystallization temperature range (about 110 to 130 ° C.) It is considered that a large amount of the resin staying for a long time tends to exist, and therefore, crystallization and crystal growth of the resin can easily proceed.

  However, even if there is a difference in the residence time of the molten resin in the cavity 35, the molten resin to be introduced is sufficiently higher in temperature than the crystallization temperature range (about 110 to 130 ° C.) (for example, 200 degrees or more). Even if the resin is injected into a portion of the cavity 35 that is far from the resin inlet, the flow of the resin while flowing in the cavity 35 is not less than the crystallization temperature region, so the flow is completed. The difference is reduced and the change in the amount of crystal formation is reduced. For this reason, even if there is a difference in residence time between the resin injected into the part of the cavity 35 far from the resin inlet and the resin injected into the part near the resin inlet, the temperature of the introduced resin is high (for example, 200 ° C. It is considered that the difference in the amount of crystal formation and crystal growth between the two is smaller.

Therefore, the temperature of the resin injected into the cavity 35 of the injection mold 25 is 180 ° C. or higher, preferably 200 ° C. or higher, more preferably 220 ° C. or higher, and particularly preferably 240 ° C. or higher. The difference (variation) in resin crystal generation amount and crystal size in the metal mold 25 becomes small. Then, the hot preform 40 released from the injection mold 25 has a difference in fine crystal production amount and crystal size due to rapid cooling of the portion far from the resin inlet of the cavity 35 and the portion close to the resin inlet. In the stretch blow molding process, the preform 40 is heated to a temperature close to the crystallization temperature (for example, 120). In the heating stage of stretch blow molding, the resin only softens and does not melt, and most of the crystals in the preform 40 remain stretch blown and cooled. Become. Then, since the crystal structure of the preform 40 does not change and the process proceeds to the stretching process, the thickness of the obtained transparent bottle and the uniformity of transparency (non-uniformity) are almost determined at the stage of forming the preform 40. . Therefore, the crystal structure (crystal amount, crystal size, etc.) of the preform 40 is made uniform, in other words, the resin temperature at the exit of the runner portion injected into the injection mold 25 is increased to 180 ° C. or higher. is important. In the production example of the transparent bottle of the present invention, it is considered that a transparent bottle with uniform transparency is obtained by such a principle. In addition, if the crystal structure of the preform 40 is uniform, it is considered that the thickness uniformity of the transparent bottle obtained by stretch blow molding has a positive influence.

  When forming a preform by cooling a high-temperature resin of 180 ° C. or higher with the injection mold 51, the resin temperature at the central portion in the thickness direction of the hot preform 40 immediately after the mold release remains high. In order to maintain the shape of the preform 40 immediately after the mold release, it is necessary to relatively sufficiently cool the surface portion, cool it to the inside, and thicken the solidified portion near the surface. Then, since the amount of fine crystals generated by rapid cooling in the injection mold 25 is relatively large, the ratio of fine crystals in the preform after cooling to room temperature is increased, and the transparency when a transparent bottle is used. It is thought that there is also an effect of improving.

(Hot Parison type stretch blow molding)
Next, a method for producing a transparent bottle when the transparent bottle 10 made of a polypropylene resin is produced by hot-parison type injection stretch blow molding will be described. The hot parison type injection stretch blow molding is not greatly different from the cold parison type injection stretch blow molding. The hot parison type injection stretch blow molding is characterized by the cold parison type injection stretch blow molding, in which the hot preform 40 released from the injection mold 25 is stretched and blow molded as it is without being cooled. Is a point. In this case, since the heating energy to the preform 40 in stretch blow molding can be saved, the manufacturing method is excellent in terms of energy efficiency.

  FIG. 7 is a schematic diagram for explaining a method of manufacturing the transparent bottle 10 by hot Parison type injection stretch blow molding. In the cold parison type injection stretch blow molding, as shown in FIGS. 2 to 4, the injection molding process and the blow molding process of the preform 40 are completely separated and taken out from the injection mold 25. The preform 40 is once cooled to room temperature, and heat treatment from room temperature is performed at the time of stretch blow molding. On the other hand, in the hot parison type injection stretch blow molding, as shown in FIG. 7, the heat applied to the resin at the time of the injection molding process is used, and the hot mold taken out from the injection molding die 55 is used. The preform 60 is directly introduced into the stretch blow molding process.

  A hot parison type injection stretch blow molding will be described in detail with reference to FIG. First, the hot preform 60 is formed in the injection mold 55 of the injection molding machine 50 in the same manner as the cold parison type injection stretch blow molding. The hot preform 60 formed in the injection molding die 55 is removed from the injection molding die 55 without cooling more than necessary, and the hot preform 60 is mounted on the stretch blow device 66 as it is. The hot preform 60 is subjected to heat treatment and stretch blow molding.

  In FIG. 7, a is a step of mounting the hot preform 60 on the stretch blow device 66, b is a step of further heating the mounted hot preform 60 to a stretch blow molding temperature, and c is a stretch blow molding temperature. A step of longitudinally stretching the heated hot preform 60 by a stretching rod 69 and a transverse direction blowing by air blowing, d is a blow molding of the transparent bottle 10 after the stretch blow molding is finished and cooled This is a process of releasing from the mold 62. The description of each step in the hot parison type stretch blow molding is the same as the cold parison type stretch blow molding, but in the case of the hot parison type stretch blow molding, the temperature of the preform 60 before being heated remains high. Accordingly, the heating load and heating time of the heater 65 are reduced accordingly.

The temperature profile of hot parison type injection stretch blow molding will be described with reference to FIG. In the hot parison type stretch blow molding, the process of forming the hot preform 60 in the injection mold 55 is the same as the cold parison type. In hot parison formula stretch blow molding, Figure 5 illustrates a is cooling step is omitted from the temperature t ₂ of the preform 40 to room temperature in the cold parison type injection stretch blow molding, is formed in the injection mold 55 As shown in FIG. 8, when the hot preform 60 is cooled in the injection molding die 55 and can be released from the hot preform 60 (resin temperature t ₄ ), the hot preform 60 is used for injection molding. The mold 55 is released from the mold 55 and immediately inserted into the heater 65 of the stretch blow molding machine 66 and heated as it is to a predetermined temperature (resin temperature t ₃ ). After heating, the preform 60 is stretch blow molded in the same manner as the cold parison stretch blow molding to produce the transparent bottle 10. Normally, the resin temperature t ₄ is often hotter than the resin temperature t ₂ in FIG.

  Here, it should be noted that, as described in the cooling temperature of the preform in the cold parison type stretch blow molding, the hot preform 60 is temporarily reduced to a temperature below the crystallization temperature (for example, It is preferable to cool to 110 degrees or less, preferably 100 degrees C or less. Moreover, it is preferable to cool the hot preform 60 as quickly as possible. By doing in this way, also in hot parison type | mold stretch blow molding, manufacture of a transparent bottle with high transparency and few variations of transparency becomes easy.

(Transparent bottle shape design)
By carrying out the stretching treatment (stretch blow molding) as described above, the thickness of the body portion of the preform is reduced, and in the state where the transparent bottle 10 is finally formed, the thickness t is 0.85 mm or more. 1.6 mm. The thickness of the barrel portion of the transparent bottle 10 is determined by the thickness of the preform barrel (approximately determined by the thickness of the cavity of the injection mold and the injection amount of the resin) and the stretch blow mold. It is determined by the shape of the cavity. Since the cavity of the injection mold is stretch blow molded except for the neck, it is preferable that the cavity is not a complicated shape but a cylindrical shape. Since the shape of the cavity of the stretch blow molding die is to form the final outer diameter of the transparent bottle 10, it is formed into a target shape. In addition, the thickness of the trunk | drum of the transparent bottle 10 may be represented by the draw ratio of each length and breadth with respect to the preform 60 before stretch blow molding, and about 1.5 to 5 times each of length and width is preferable.

(Physical properties of transparent bottles, etc.)
The wall thickness t of the transparent bottle 10 can be measured by any measuring device such as a mechanical thickness meter such as a micrometer or an optical thickness meter. The haze value of the transparent bottle 10 is measured according to JIS K7105. The buckling strength of the transparent bottle 10 is measured by applying the compression pressure from the top and bottom of the transparent bottle 10 until the buckling is performed, similarly to the buckling strength test of the PET bottle. For the buckling strength test, a commercially available compression tester (for example, Autograph AG-1 manufactured by Shimadzu Corporation) may be used.

[Measurement of physical properties of transparent bottles]
(Wall thickness of transparent bottle)
The thickness of the transparent bottle is measured with a micrometer by cutting out a relatively flat portion of the body 11 excluding a portion of about 5 mm from the upper and lower corners 15 and 16 of the transparent bottle 10 in FIG. When a plurality of locations are taken out from the same transparent bottle and the thickness (mm) is measured, the average value thereof is taken as the thickness of the transparent bottle. In this experiment, as a general rule, three transparent bottles are prepared, and three pieces at relatively distant positions on the body of each transparent bottle are cut out, and a specimen for measuring the thickness and measuring the haze value described later. It was.

(Haze value and normalized haze value of transparent bottle)
The haze value of the transparent bottle is measured according to JIS K7105. The test piece was measured using the same test piece as that measured for the wall thickness. When three places are cut out from the same transparent bottle and the haze value is measured, the average value thereof is calculated and set as the haze value of the transparent bottle. For the normalized haze value, “haze value (%)” / “thickness (mm)” (% / mm) is calculated from the thickness and haze value, and the average value is calculated for each transparent bottle.
(Dispersion of haze value and normalized haze value of transparent bottle)
When measuring variation in haze value, at least three portions that are estimated to have large variation in haze value by visual observation of one transparent bottle or separated from each other are cut into test pieces. Calculates the thickness and haze value at three locations, the average value and the deviation of the normalized haze values, and calculates the ratio of the haze values at each of the two locations (smaller haze value / larger haze value) To do.

[Production Example 1]
Cold parison type injection stretch blow molding machine (KINGSTRONG M & E TECNOLOGY CO., LTD ECOJET 180B52 type injection molding machine) using polypropylene resin (propylene-ethylene random copolymer: Prime Polymer J721-GR (trade name)) (Trade name) and SPLY800 TECNOLOGY LIMITED SPRA800HF2 type biaxial stretch blow molding machine (trade name)), using an elliptical columnar shape as shown in FIG. A plurality of transparent bottles 10 were prepared. The resin temperature of the cylinder part is a set temperature of the heating cylinder 22 of the injection molding machine, and the hot runner part resin temperature is a direct measurement of the resin temperature near the outlet of the hot runner part immediately after the end of injection molding.

(Injection molding conditions)
Injection molding resin amount: about 27g
Injection molding (hot runner) temperature: 180 degrees Heating cylinder temperature: same as hot runner temperature Injection molding pressure: 5.5 MPa
Hot preform release temperature: 100 ° C
Injection mold (cooling water) temperature: 15 ° C
Mold cooling time for injection molding: 15 seconds Cooling of preform after mold release: Cooling at room temperature (stretch blow molding conditions)
Cavity capacity: 200ml
Heating temperature: 135 ° C
Stretch ratio: 2.0 times in length and 2.0 times in width

  A plurality of transparent bottles 10 having a shape close to the shape shown in FIG. As for each transparent bottle 10, the difference in thickness and transparency was hardly recognized by visual observation. Any three of them were sampled for testing. A test piece was cut out from two sampled upper and lower parts on the front side of the body 11 of each transparent bottle 10 and one place on the back side central part. The thickness and haze value of each test piece were measured and shown in Table 1. Based on the measured values of the thickness and haze value for each transparent bottle 10, the average value of the thickness and haze value for each transparent bottle 10, the normalized haze value, the average value thereof, and the deviation of the normalized haze value, transparent The ratio (small value / large value) of the two haze values for each bottle 10 was calculated and shown in the column of the molding temperature 180 ° C. in Table 1 for each transparent bottle.

[Production Examples 2 to 8]
Production Examples 2 to 8 are the same as Production Example 1 except that the molding temperature (hot runner temperature) was changed from 180 ° C. to 200 ° C., 220 ° C., 237 ° C., 240 ° C., 260 ° C., 280 ° C., and 300 ° C., respectively. Transparent bottles were produced in the same manner as in Production Example 1, and in the same manner as in Example 1, three transparent bottles in each production example were used as samples, and test pieces were cut out from each of the transparent bottles at three locations to obtain the thickness and haze value. The average value of the thickness and haze value for each transparent bottle, the normalized haze value and its average value, the deviation of the normalized haze value, and the ratio of the haze values at two locations for each transparent bottle (small value / large value) Value) was calculated and shown in Table 1 in the same manner as in Production Example 1. However, in Manufacturing Example 4 (manufacturing example with an injection molding temperature of 237 ° C.), the cylinder resin temperature is set to 235 ° C., which is 2 ° C. lower than the hot runner temperature. In Table 1, the evaluation data of Production Example 4 is bottle no. There is only one of 1. Bottle no. The evaluation data of the two transparent bottles 2 and 3 are evaluation data of the transparent bottles of Production Examples 8 and 9, which will be described later.

[Comparative example: Measurement of physical properties of commercially available PP transparent bottle]
Similar to Production Example 1 using a commercially available PP transparent bottle (Nikko Hansen, trade name, JP bottle JP-250), which is currently available and relatively thick and considered to be the most transparent. The thickness and the haze value are measured, and the average value of the thickness and haze value for each transparent bottle 10, the normalized haze value, the average value thereof, the deviation of the normalized haze value, and the transparent bottle 10 each at two locations The haze value ratio (small value / large value) was calculated and shown in Table 1 in the same manner as in Production Example 1.

  Transparent bottles produced according to Production Examples 1 to 8 have a haze value of 6.0% or less and a normalized haze value of less than 5.0 when the preform 60 is molded at an injection molding temperature (hot runner temperature) of 180 to 300 ° C. It can be seen that a transparent bottle can be manufactured. In particular, a transparent bottle having a high transparency can have a haze value of about 1.5%. Most of the transparent bottles have a haze value of 1.5 to 4.0% and a normalized haze value of 3% or less, and a transparent bottle having very excellent transparency can be produced. On the other hand, a transparent bottle molded at a molding temperature (hot runner temperature) of 180 degrees has a haze value of 6.0% or less, a normalized haze value of less than 5.0, and a difference in normalized haze values of 1.6% / mm or less. May satisfy the standard values of the present invention of the present application, but may deviate from these standard values. Moreover, although the transparent bottle shape | molded at 300 degreeC may satisfy the specification value of this invention, it may remove | deviate from these specification values. The commercially available transparent bottles did not satisfy the standard values of a haze value of 6.0% or less, a normalized haze value of less than 5.0, and a normalized haze value deviation of 1.0 or less.

[Production Example 9]
In the same manner as in Production Example 4, a hot preform was formed in the cavity of the injection mold, and the hot preform released from the mold was immediately immersed in cold water for cooling treatment. The preform forcibly cooled to room temperature was stretch blow molded in the same manner as in Example 1 to produce a transparent bottle 10. Using one of the transparent bottles 10 as a sample, the thickness and haze value are measured in the same manner as in Production Example 1, and the average value of the thickness and haze value, the normalized haze value, its average value, deviation, and the transparent bottle The ratio (small value / large value) of the haze values at two locations in each of 10 was calculated, and Table 1 shows the bottle no. It was shown as 2.

[Production Example 10]
In Production Example 4, the transparent bottle 10 was produced in the same manner as in Production Example 4 except that the cooling time of the hot preform 60 in the cavity of the injection mold was 120 seconds. The surface temperature of the preform immediately after being released from the injection mold was 80 ° C. or less. Using one of the transparent bottles 10 as a sample, the thickness and haze value are measured in the same manner as in Production Example 1, and the average value of the thickness and haze value, the normalized haze value, its average value, deviation, and the transparent bottle The ratio (small value / large value) of the haze values at two locations in each of 10 was calculated, and Table 1 shows the bottle no. It was shown as 3.

  As shown in Table 1, in Production Examples 9 and 10, the haze value of the transparent bottle 10, the average value of the haze value, the normalized haze value and its average value, deviation, and the ratio of the two haze values of the transparent bottle 10 The transparent bottle 10 with higher transparency than the transparent bottle 10 of Production Example 4 was obtained. Moreover, the transparent bottle 10 of the manufacture example 9 obtained the transparent bottle with a variation in transparency smaller than the transparent bottle 10 of the manufacture example 4.

  FIG. 9 shows the relationship of the haze value with respect to the thickness of each transparent container in Table 1. FIG. 10 shows the normalized haze value (average value) with respect to the injection molding temperature (hot runner temperature) in each transparent container production. And the range of variation). From FIG. 9 and FIG. 10, it is well understood that when the injection molding temperature (hot runner temperature) is set to 180 to 300 ° C., a transparent container having a small haze value and a normalized haze value and a small variation thereof is manufactured. In particular, from FIG. 10, when a transparent bottle is produced at an injection molding temperature of 220 to 280 ° C., the normalized haze value between the bottles as compared to a transparent bottle produced at an injection molding temperature of 180 to 200 ° C. or 300 ° C. It can be seen that the variation in the size is also small. It can be seen that transparent bottles manufactured at an injection molding temperature of 220 to 260 ° C. have particularly small variations in normalized haze values between the bottles. A transparent bottle with a wall thickness of 0.85 mm or more, a normalized haze value of less than 5.0 / mm, and a variation in transparency expressed as a deviation of the normalized haze value of 1.0% / mm or less is It is a transparent bottle that can be produced for the first time according to the invention.

DESCRIPTION OF SYMBOLS 10 Transparent bottle 11 Trunk part 12 Neck part 13 Shoulder part 14 Bottom part 15 Shoulder part and corner part 16 of a trunk part Bottom part and corner part 17 of a trunk part Recess 20 Injection molding machine 21 Injection molding machine main body 22 Heating cylinder 23 Extrusion screw 24 Hopper 25 Injection mold 26 Fixed die plate 27 Moving die plate 28 Hot runner 29 Heater 30 Resin pellet 31 Molten resin in heating cylinder 32 Molten resin in hot runner 33 Resin in cavity 35 Cavity 40 Preform (Parison)
41 Heat Preform 42 Longitudinal Preform 43 Vertical Stretch Preform 44 Biaxial Stretch Molded Body 45 Heater 46 Stretch Blow Molding Device 47 Stretch Blow Molding Die 48 Cavity 49 Stretch Rod 50 Injection Molding Machine 52 Heating Cylinder 53 Extrusion Screw 54 Hopper 55 Injection mold 56 Fixed die plate 60 Preform (hot parison)
61 Heat Preform 62 Stretch Blow Preform 65 Heater 66 Stretch Blow Molding Device 67 Stretch Blow Molding Die 68 Cavity 69 Stretch Rod

Claims (6)

An injection stretch blow bottle made of a polypropylene resin composition,
The resin component of the polypropylene resin composition is isotactic polypropylene and / or propylene-olefin copolymer,
The body thickness is 0.85 to 1.6 mm,
The haze value ratio (hereinafter referred to as normalized haze value) to the wall thickness of the trunk is less than 5.0% / mm,
An injection stretch blow bottle having a haze value of 6.0% or less.   2. The injection according to claim 1, wherein a deviation of the normalized haze value at each position from an average value of the normalized haze values at any three positions of the body portion is 1.0% / mm or less. Stretch blow bottle.   The injection stretch blow bottle according to claim 1 or 2, wherein a ratio (small value / large value) of haze values at any two locations of the body portion is 0.5 or more.   The injection stretch blow bottle according to any one of claims 1 to 3, wherein the propylene-olefin copolymer contains ethylene as an olefin.   The body is a substantially cylindrical shape, a substantially elliptical column, a polygonal column having a substantially polygonal cross section, or a polygonal column having a substantially polygonal cross section and smooth corners. Item 5. The injection stretch blow bottle according to any one of Items 1 to 4.   The injection stretch blow bottle according to any one of claims 1 to 5, wherein the resin component of the polypropylene resin composition is produced mainly from a biomass raw material.

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