JP3264771B2 - Opaque laminated resin film with excellent printability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an opaque laminated resin film having fine pores therein, which is excellent in offset printability and computer printing such as a dot printer and a fusion heat transfer printer. The resin film is also useful as outdoor poster paper, sticker paper, etc., as well as water-resistant label paper and book paper.

[0002]

2. Description of the Related Art Synthetic paper having fine pores formed by stretching a thermoplastic resin sheet containing calcium carbonate powder (JP-B-60-36173, JP-B-1-5609)
No. 1) is superior in water resistance and strength to paper obtained by making pulp, and is therefore used in election poster paper, vending machine stickers, outdoor large advertising posters, drums and gas cylinders. It is used for management labels such as iron and steel sheets, labels for detergent bottles and frozen foods, tacks for air luggage, etc., and for paper such as books read in a bath.

[0003] Void whitening synthetic paper obtained by using these calcium carbonate as a porogen for stretching a resin film is based on a polyolefin-based synthetic resin such as polypropylene or polyethylene having a non-absorbent matrix. Therefore, compared with pulp paper, there is a drawback that the drying properties of printing ink, ribbon ink of a dot printer, etc. are poor, and the surface strength of the laminated film is also weak. In order to solve these problems, the surface of this polyolefin synthetic paper is coated with a pigment coating material (usually composed of a filler such as clay or silica and a binder such as polyvinyl alcohol or styrene / butadiene latex). Paper is used.

[0004]

In the case where a pigment coating layer is provided on the surface to improve the ink drying property, there is a problem in terms of economy because the number of steps is increased. SUMMARY OF THE INVENTION An object of the present invention is to economically provide synthetic paper having good ink drying properties and no printing trouble and high opacity.

[0005]

According to the present invention, there is provided a polypropylene resin of 65 to 95% by weight, and a heavy calcium carbonate having a particle diameter of 1 to 6 μm obtained by a pulverization method of 35 to 5% by weight.
The base resin layer (A) composed of a stretched film containing a large number of fine pores inside a film obtained by stretching a polypropylene resin film containing: 35 to 70 weight parts of a polypropylene resin on one surface or both surfaces %, Sedimentable light calcium carbonate having a particle size of 0.5 to 3 μm
The present invention provides an opaque laminated resin film having an opacity of 80% or more, comprising a surface layer (B) comprising a stretched film of a polypropylene-based resin film, the opaque laminated resin film containing 80% by weight. Hereinafter, the present invention will be described in more detail.

(Polypropylene Resin) The polypropylene resin is mainly composed of propylene homopolymer, propylene, ethylene, butene-1, hexene
Copolymers with α-olefins such as 1, heptene-1, 4-methylpentene-1 are used. This copolymer is
It may be a random copolymer or a block copolymer. Preferably, the melt flow rate (JIS K-7)
210; 230 ° C., 2.16 kg load) 0.5 to 50
g / 10 minutes, a crystallinity (X-ray method) of 20% or more, more preferably 40 to 75%, and a melting point of 140 to 190 ° C.

(Heavy Calcium Carbonate) Limestone is finely pulverized with a hammer mill or the like, and the accumulated weight is measured by a laser diffraction particle size analyzer “Microtrack” (trade name, manufactured by Nikkiso Co., Ltd.).
% Is 1 to 6 μm, preferably 3 to 4 μm
Heavy calcium carbonate classified and sieved is used.
If it is less than 1 μm, there is a problem in economics and it is not practical, and if it is more than 6 μm, the synthetic paper obtained will have low stiffness (rigidity), and wrinkles will occur during label processing, Paper feedability during printing is reduced. Specific surface area of heavy calcium carbonate [measured with constant pressure aeration type specific surface area measuring device SS-100 (trade name) of Shimadzu Corporation]
Is from 10,000 to 34,800 cm ² / g;
ET method [N ₂ gas adsorption method] The specific surface area is 4 m ² / g to 1
Those having ² m ² / g are preferred.

(Precipitable calcium carbonate) A method of injecting carbon dioxide into lime milk in which quicklime is hydrated to precipitate crystalline calcium carbonate. It is obtained by a synthetic method such as a method of growing crystals by precipitation and a method of reacting calcium chloride with soda ash, and has a particle size of 0.5 to 3 µm, preferably 1 to 2 µm, measured by Microtrac.
The precipitated calcium carbonate synthesized in m.

When the particle size is less than 0.5 μm, it is difficult to stably produce a composition with a polypropylene resin because of its low bulk density. The effect of improving the drying properties of the ink and the ribbon ink of the dot printer is only slightly recognized. The specific surface area of the precipitated calcium is 35,000 to 5
000 cm ² / g, BET specific surface area is 12 m
It is preferred in ² / ^{g~20m 2} / g.

(Optional components) In the practice of the present invention, other components other than the polypropylene-based resin and calcium carbonate, a heat stabilizer, an ultraviolet absorber, an antioxidant, a lubricant,
A dispersant or the like may be blended.
The weight percent or less may be replaced by high density polyethylene, linear low density polyethylene, branched low density polyethylene or the like.
Further, a slight amount of precipitated calcium carbonate may be blended in the base material layer (A), and some heavy calcium carbonate may be blended in the surface layer (B).

If the content of heavy calcium carbonate in the base material layer (A) is less than 5% by weight, sufficient opacity cannot be obtained, and
If the content is more than 10% by weight, the waist (rigidity) is weakened, and the efficiency of label processing and printing workability is reduced. When the content of the precipitated calcium carbonate in the surface layer (B) is less than 30% by weight, the effect of improving the drying property of the ink cannot be obtained, and when it exceeds 65% by weight, the composition with the polypropylene-based resin cannot be obtained. It is difficult to produce a product stably.

(Opaque laminated resin film) 65 to 95% by weight of a polypropylene resin and 35 to 5% by weight of calcium bicarbonate having a particle size of 1 to 6 μm obtained by a pulverization method
The thermoplastic resin composition containing (A) and the thermoplastic composition (B) containing 65 to 30% by weight of sedimentable calcium carbonate having a particle size of 0.5 to 3 μm are respectively separated using separate extruders. Melt kneading, inflation molding, T-
The film formed by die forming is stretched at least in a uniaxial direction at a temperature lower than the melting point of the polypropylene resin to form the opaque laminated resin film of the present invention.

The lamination may be performed before the stretching or after the stretching. Alternatively, after stretching one side, the other is laminated and stretched, and the base paper layer may be a biaxially stretched product (A) and the surface layer may be a uniaxially stretched product (B). Stretching is performed using a tenter, a mandrel, and a group of rolls in a longitudinal direction, a uniaxial direction in a lateral direction, or a biaxial direction in a longitudinal direction and a lateral direction. The draw ratio is the required quality of the target, the stretching process,
Although it depends on the type of material, it is generally stretched 4 times to 12 times in the tenter method, 1.3 times to 4 times in the mandrel method, and 2.5 times to 7 times in the roll method.

The stretching temperature is lower by 3 to 20 ° C. than the melting point of the polypropylene resin (A). For example, in the case of propylene homopolymer (melting point: 167 to 174 ° C.), the stretching temperature is 147 ° C.
To 171 ° C, preferably 150 to 160 ° C. The surface of the stretched laminated resin film is subjected to a sizing treatment, a corona discharge treatment, or the like as necessary. This opaque laminated resin film has a porosity calculated by the following formula (1) of 20 to 70%, preferably 2 in the film of the base material layer (A).
Opacity (JIS P)
-8138) is 80% or more, preferably 90 to 100%
This is an opaque laminated resin film that has a high ink drying property during offset printing, does not cause a problem of paper dust, and has a quick drying property for ribbon ink of a dot printer.

[0015]

(Equation 1)

If the porosity is less than 20%, the opacity of the synthetic paper is not sufficient. If the porosity is more than 70%, the rigidity of the synthetic paper is weakened, and the efficiency of label processing and printing work is reduced. Also, if the opacity of the laminated resin film is less than 80%, when reading the bar code of the management label affixed to a drum, gas cylinder, steel plate, or the like, the base material can be seen through. The contrast with the code is reduced, and an error occurs in reading the barcode.

The thickness of the surface layer (B) of the laminated resin film is 1 μm or more, preferably 2 to 60 μm, and is 50% or less, preferably 3 to 50% of the total thickness of the synthetic paper.
When it is less than m, the effect of improving the ink drying property is small, and when it exceeds 50% of the total wall thickness, the proportion of the high cost precipitated calcium carbonate in the synthetic paper increases, which is not economical. The thickness of the base material layer (A) is 20 to 300 μm, preferably 40 to 200 μm. The thickness of the synthetic paper varies depending on the application, but is 30 to 420 μm, preferably 50 to 300 μm.
μm.
Synthetic paper having a thickness of 840 μm is used as a playing card or a packaging board.

[0018]

The present invention will be described below with reference to examples. (Example 1) Melt flow rate (MFR) is 0.8 g
/ 10 min propylene homopolymer "Mitsubishi Polypro MA-
8 "(trade name, manufactured by Mitsubishi Yuka Corporation) (melting point: 167 ° C)
75% by weight, 50% weight cumulative particle size measured by Microtrac is 3.5 μm, and specific surface area is 16,000 cm ²
/ G heavy calcium carbonate "Softon 1800" (trade name, manufactured by Bihoku Powder Co., Ltd.) 15% by weight and a high-density polyethylene having a melt index of 11 g / 10 minutes ["Mitsubishi Polyethylene JY-20A (Mitsubishi Oil)" (Trade name) manufactured by Kayaku Co., Ltd.]
After melt-kneading at a temperature of 0 ° C., it is extruded into a film through a die set at 250 ° C., and cooled to about 60 ° C.
To the temperature of

After the film was heated again to 145 ° C., it was stretched 5 times in the machine direction by utilizing the difference in peripheral speed of the roll group. Propylene homopolymer "Mitsubishi Polypro MA-3" having a melt flow rate of 10 g / 10 min [Mitsubishi Yuka Corporation
(Trade name)] (melting point 167 ° C.) 50% by weight, 50% weight cumulative particle size measured by Microtrac 1.5 μm,
Precipitable calcium carbonate having a specific surface area of 39,000 cm ² / g “Brilliant 15” (trade name, manufactured by Shiraishi Industry Co., Ltd.) 45% by weight, and a melt index of 11 g /
A composition consisting of 5% by weight of high-density polyethylene for 10 minutes is melt-kneaded at 270 ° C. using an extruder to form a T-
The film was extruded from a die and melt-pressed on both sides of the longitudinally stretched film with a roll to obtain a laminate having a three-layer structure.

After the laminate was heated to 155 ° C., it was stretched 8.5 times in the transverse direction using a tenter, and 158
Annealing treatment was performed at a temperature of ° C. Next, after cooling to 60 ° C., the ear portion was slit to obtain an opaque laminated resin film having a three-layer structure of B / A / B (20 μm / 50 μm / 20 μm). The opacity of the obtained opaque laminated resin film was 91%, and the porosity of the base material layer (A) was 35%. The dryness of the ink ribbon of the dot printer is 5
After a minute, there was no practical problem, and after 10 minutes, the film was completely dried quickly. Also, the suitability for offset printing is that no double-sheet insertion (a problem of supplying two sheets at the same time) occurs at all,
The ink drying property was good, as fast as 2 hours.

Measurement Method (Ribbon Ink Drying Property of Dot Printer) A dot printer “PC-PR-201V” (trade name) and an ink ribbon “PC-PR201H-01” manufactured by NEC Corporation were used for the evaluation of the laminated resin film for evaluation. (Trade name), a barcode was printed, and the printed surface was rubbed with a kanakin cloth every 5 minutes to evaluate the ink drying property.

The judgment was made based on the following criteria. ：: Since the ink was already dried within 10 minutes, no trace of the spread of the print was generated even when rubbed. Δ: Evaluated after 10 minutes, traces of spreading of the print were slightly generated, but there was no problem in practical use. ×: There is a widespread trace of rubbing and spread of the print in the evaluation after 10 minutes, and there is a problem in practical use.

(Offset printing suitability) The evaluation film was cut into a quarter-cutting film (length 788 mm, width 545 mm).
Toyo Ink Co., Ltd. offset ink "TSP-40"
0 "(trade name) and offset 2 manufactured by Mitsubishi Heavy Industries, Ltd.
Using a color printing machine "Diamond printing machine" (product name), 1 per minute
Two-color printing was performed on 2,000 sheets at a printing speed of 00 sheets, and workability (paper feedability) and ink drying property were evaluated. The judgment was made according to the following criteria.

Workability (paper feedability) ○: No problem at all △: Two sheets are inserted (two sheets are supplied at the same time), but there is no problem in practical use ×: Two sheets are inserted, and there is a problem in practical use

Drying A : When the printed material was pressed with a finger, the ink printed on the fifth film from the top did not adhere to the back side of the fourth film from the top within 3 hours. Δ: Similarly, it did not stick within more than 3 hours and within 5 hours. ×: In the same manner, it is applied even if it exceeds 5 hours (it backs out).

(Comparative Examples 1 and 2) A laminated resin film was produced in the same manner as in Example 1 except that the type of calcium carbonate used in Example 1 was changed to calcium carbonate shown in Table 1. The ink ribbon drying property and offset printing property were evaluated. Table 1 shows the results.

(Examples 2 to 3 and Comparative Examples 3 to 7) Except that the particle size of calcium carbonate used in Example 1 and the compounding amount of the resin and calcium carbonate were changed to the particle size and compounding amount shown in Table 1, A laminated resin film was prepared in the same manner as in Example 1, and the drying properties of the ribbon ink and the offset printing property of the dot printer were evaluated. Table 1 shows the results.

Example 4 Melt Flow Rate (MF)
R) was 80% by weight of a propylene homopolymer (melting point: 167 ° C.) of 0.8 g / 10 min.
0% weight cumulative particle size is 3.5 μm, specific surface area is 16,000
After melt-kneading a composition (A1) comprising 10% by weight of heavy calcium carbonate of 0 cm ² / g and 10% by weight of high-density polyethylene having a melt index of 11 g / 10 minutes at a temperature of 260 ° C. using an extruder. The film was extruded into a film through a die set at 250 ° C., and cooled to a temperature of about 60 ° C. by a cooling roll. Repeat this film 14
After heating to 5 ° C., the film was stretched 5 times in the machine direction by utilizing the peripheral speed difference of the roll group.

A propylene homopolymer (melting point: 167 ° C.) having a melt flow rate of 10 g / 10 min.
m, 45% by weight of precipitated calcium carbonate having a specific surface area of 39,000 cm ² / g, and a melt index of 11 g
Composition (B) consisting of 5% by weight of high-density polyethylene of / 10 minutes, 45% by weight of polypropylene (melting index: 167 ° C.) having a melt index of 11 g / 10 minutes, and a particle size of 3.5.
A composition (A2) consisting of 50% by weight of heavy calcium carbonate having a particle size of 50 μm and 5% by weight of a high-density polyethylene having a melt index of 11 g / 10 minutes is melt-kneaded by separate extruders and laminated in a die. The co-extruded sheet is laminated on both sides of the longitudinally stretched film so that (B) is on the outside,
Then, after cooling to 60 ° C., it is heated to about 160 ° C., stretched 7.5 times in the transverse direction with a tenter, annealed at 165 ° C., cooled to 60 ° C., slit the ears, and has a five-layer structure (B / A2 / A1 / A2 / B) to obtain an opaque laminated resin stretched film.

The thickness of this is B / A2 / A1 / A2
/ B = 3μ / 20μ / 45μ / 20μ / 3μ, the total amount of heavy calcium carbonate in the base material layer (A2 / A1 / A2) is 30% by weight, and the average porosity is 30%. The opacity of the obtained laminated resin film was 97%.

[0031]

[Table 1]

[0032]

According to the present invention, a synthetic paper having good drying properties of the offset printing ink and good paper supply / discharge properties can be obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-251793 (JP, A) JP-A-4-59225 (JP, A) JP-A-4-18338 (JP, A) 74577 (JP, A) JP-A-63-193836 (JP, A) JP-A-7-102096 (JP, A) JP-B-54-17789 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. A film obtained by stretching a polypropylene resin film containing 65 to 95% by weight of a polypropylene resin and 35 to 5% by weight of heavy calcium carbonate having a particle diameter of 1 to 6 μm obtained by a pulverization method. Precipitable light calcium carbonate having 35 to 75% by weight of a polypropylene-based resin and a particle size of 0.5 to 3 µm on one or both sides of a base layer (A) composed of a stretched film containing a large number of fine pores inside the film. An opaque laminated resin film having an opacity of 80% or more, obtained by laminating a surface layer (B) composed of a stretched film of a polypropylene resin film containing 65 to 30% by weight.