JPH037318A - Foamable thermoplastic resin and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce charging rate in a containing box such as a paper box by providing foamable thermoplastic resin having a S shape and specific values of dimensional ratio and density. CONSTITUTION:Foamed thermoplastic resin fine stripe extended and foamed from a base having a plurality of fine holes of semicircular, circular, square, elliptical or semielliptical shape or other opening shape attached to the end of an extruder is cooled, and then cut obliquely to an extruding direction. The cut stripe is heated, refoamed, and bent in a three-dimensional manner thereby to obtain bulk buffers. The foamed resin has a density =0.005-0.05g/ml. When its central thickness is Tl, the thickness of bent end is T2, the whole width indicating a curvature is Y, the length of the buffer is L and the width of the buffer is W, the real size of the length L is 30-100mm with the size for satisfying T1/L = 0.1-0.6, W/L = 0.2-0.5, Y/L =-0.4-1.5, Y/W = 1.2-5.0 and T1/T2>2.

Description

[Detailed Description of the Invention] (Industrial Application Field) When a packaged object of an arbitrary shape is housed in a regular package such as a cardboard box, a gap is created between the packaged object and the package, resulting in poor stability. The packaged items will be damaged during transportation. In order to prevent these problems, a packaging form in which so-called loose M1 bodies made of small pieces of thermoplastic resin foam or the like are stuffed into the gaps has been widely adopted.

The present invention relates to a bulk cushioning body made of thermoplastic resin foam, and more particularly to a three-dimensionally curved bulk cushioning body different from the shape of conventional products, and a method for manufacturing the same.

(Prior Art) Conventional loose shock absorbers include a three-dimensionally curved string-like shape having a short fiber structure with a circular cross section as disclosed in Japanese Patent Publication No. 42-4512, and Japanese Patent Application Laid-Open No. 59-187566. The string-like shape with an irregular cross section disclosed in Japanese Patent Publication No. 47-30102, Japanese Utility Model Publication No. 57-58141
A shape with relatively little three-dimensional curvature is known, as disclosed in Japanese Patent Publication No.

(Problems to be Solved by the Invention) The curved string-like loose cushioning bodies of the prior art have the following disadvantages because the cushioning bodies are individually entangled with each other before use. In other words, during use, if the space gap between the wall of the storage container such as a paper box and the packaged item is narrow, large intertwined strings [51
It took a lot of effort to separate the body comrades into smaller parts. Also, if you apply force and pull to untangle the string, it will break and become shorter.
As a result, the curvature of the string was reduced and the three-dimensional filling effect was reduced.

Special Publication No. 47-30102, Publication No. 57-5814
Another conventional loose buffer body disclosed in Publication No. 1 is as follows:
There is less entanglement between the individual cushioning bodies, and compared to string-like cushioning bodies, handling is easier. However, on the other hand, it is uneconomical that the amount of filling into a storage container such as a paper box inevitably increases during use. Furthermore, when the packaging box is moved, the cushioning body tends to move due to the movement of the cargo, reducing the cushioning effect on the packaged articles.

Furthermore, in the production of conventional bulk Y1 blocks of thermoplastic resin foam, as disclosed in Japanese Patent Publication No. 47-30102 and Japanese Patent Application Laid-Open No. 59-187566,
A molten thermoplastic resin containing a foaming agent is extruded into the atmosphere through a nozzle with a large number of small-diameter extrusion holes attached to the tip of the extruder, and the extrudate is immediately introduced into cooling water for rapid cooling to prevent foaming. After cooling to below 40°C, it is shredded into a predetermined length and turned into expandable pellets.Then, the expandable pellets are reheated with high-temperature steam to re-foam and obtain a product. However, there was a drawback in that it required a rapid cooling process in water, which was a difficult and uneconomical process to manufacture.

The present invention has been made to solve the above problems all at once, and its purpose is (a) to have a large three-dimensional curvature, less entanglement of loose MWk bodies with each other, and good workability during packaging; (b) It has a high filling efficiency, that is, the amount of filling used during packaging is small, and it has a sufficient buffering function, resulting in less cargo movement. (c) It is easy to manufacture and can be economically used in a wide range of areas.

The present invention provides an improved thermoplastic resin foam that can meet these properties and a method for producing the same.

(Means to solve the problem) The content of the invention will be explained in detail using drawings.

The thermoplastic resin foam of the present invention has a density=range of 005 to 0.
．． 05g/mL, and has a three-dimensionally curved shape as shown in Figures 1, 2, and 3. This is a sketch diagram of the direction plane viewed from the horizontal direction, where TI is the thickness at the center, T2 is the thickness at the curved tip, Y is the overall width indicating the degree of curvature, and shi is the loose shape M.
In Fig. 1, W indicates the molding width of the rose-shaped Enoki W body when viewed from the top surface.

The actual length is 30 to 100 degrees, and TI/SI = 0
．． 1-0.6, W/L=0. 2~Region 5, Y/L=0
．． 4-1. 5, Y/W=1. 2~5゜0, T
The present invention is characterized in that the object of the present invention described above is achieved by exhibiting a shape having dimensions that satisfy +/T 2 > 2.

In the above characteristic values, the density of the foam is 0.05g/
m2 or more, the foam is too hard and may cause scratches on the packaged goods, and the filling efficiency, which will be described later, is low and the amount used is large, making it uneconomical.
/mu or less, the strength, elasticity, etc. of the bulk shock absorber decreases L
, [A drawback arises in that the impact resistance also decreases.

If L is less than 3'O1m, it will be too small to fill the gap between the storage container such as a box and the packaged item with loose M blocks, resulting in poor filling efficiency and uneconomical conditions; The disadvantage is that cargo movement tends to occur during transportation, and that the yI impact effect is reduced.

TI/L is 0. If it is less than 1, the loose M1 body will break easily, and if it is more than 0°6, the curvature will decrease and the filling efficiency will decrease.

When TI/T2 is less than 2, it is difficult to obtain a bulky buffer with a large degree of curvature, resulting in the disadvantage that a product with a high filling efficiency cannot be obtained.

If W/L is less than 0.2, the loose #1iWr body is likely to break, and if it is greater than 0.5, there will be disadvantages in that cargo movement is likely to occur and filling efficiency is reduced.

Y/L is 0. Even if it is 4 or less, 1. If it is more than 5, the filling efficiency will be extremely reduced and it will be uneconomical to use, and if Y/W is 1.
．． If the number is less than 2, the goods to be packaged tend to move, and if it is more than 50, the loose 111 pieces tend to get entangled with each other.

As a result of detailed tests on the above-mentioned situation, the present invention has been able to provide an improved bulk shock absorbing body, which is the object of the present invention, by making the shape limited to the range of the above-mentioned characteristic values.

The above-described method for producing the bulk Y1 blanks of the present invention can be carried out using a semicircular, circular, square, elliptical, semi-elliptical or other shape as shown in FIGS. 7, 8 and 9 attached to the tip of the extruder. In a method for producing a thermoplastic resin foam, in which a molten thermoplastic resin containing a blowing agent is extruded into the atmosphere through a die having a plurality of open-shaped pores to obtain a foam molded article, extrusion L through these extrusion pores, After cooling, the thermoplastic resin foam strips obtained by foaming are cut diagonally at an angle of θ degrees with respect to the extrusion direction as shown in FIGS. 4 to 6 a, and the cut foam is then cut. The strips are heated and re-foamed to T7 and T above.
2. The present invention is characterized in that it obtains a loose shock absorber of the present invention having a three-dimensionally curved shape such that Y, W, and L satisfy predetermined dimensions.

In the present invention, thermoplastic resins include polystyrene resins, polystyrene resins that are mainly composed of styrene components and copolymers with unsaturated organic compounds that can be copolymerized with other styrene, and polyolefins such as ethylene, propylene, and butene. These include resins, polyolefin resins whose main components are ethylene, propylene, butene, etc., acrylic resins such as polymethyl methacrylate, polyvinyl chloride resins, and polyamide resins.

When mixed with these resins, blowing agents for forming foams include, for example, low-boiling hydrocarbons such as propane, butane, and pentane, methyl chloride, methylene chloride, monochlorodifluoromethane, dichloromonofluoromethane, dichlorodifluoromethane, Single or mixtures of halogenated hydrocarbons such as trichloromonofluoromethane and dichlorotetrafluoroethane, and mixtures of these with inorganic gases such as carbon dioxide and nitrogen are effective. The amount of these low boiling point blowing agents added varies depending on the density of the desired foam, but the amount of the above-mentioned thermoplastic resin 10
It is preferably 3 to 30 parts relative to 0 parts.

In addition, foam fill agents for adjusting the cell diameter of the foam include fine inorganic powders such as talc, calcium carbonate, and alumina, fine powders of metal soaps such as calcium stearate and zinc stearate, baking soda and citric acid, etc. A mixture of is used. These bubbles! The amount of additive added is 0.0 parts per 100 parts of the above-mentioned thermoplastic resin. 1 to 3.0 parts is preferred.

Furthermore, colorants, antistatic agents, and plasticizing agents may be added to the thermoplastic resin as necessary.

(Function) In the bulk cushioning body of the thermoplastic resin foam of the present invention and its manufacture, a screw type extruder is usually used to mix these components and extrude and foam them. That is, a thermoplastic resin, a cell regulator, etc. are fed into an extruder L, heated to a temperature higher than the softening temperature of the thermoplastic resin, kneaded by a screw rotating once, and melted and plasticized. A low-boiling point blowing agent is forced into the vent hole of the extruder using a pump, and the blowing agent is uniformly dispersed in the molten thermoplastic resin by kneading, and then the molten thermoplastic resin composition is cooled to a predetermined temperature. Thereafter, the foam is extruded into the atmosphere through a die having a large number of pores attached to the tip of the extruder to cause free foaming, thereby obtaining foam strips. The foam strips are cooled in the atmosphere, passed through a take-up roll, and then cut at a predetermined angle with respect to the extrusion direction L. The cut foam strips are led to a foaming furnace and heated with high-temperature steam. By re-foaming, a three-dimensionally curved bulk cushioning body of the thermoplastic resin foam of the present invention is manufactured.

(Example) The present invention will be described in detail below based on an example with reference to the drawings.

100 parts by weight of polystyrene with MFR=5 and talc 1.0
After mixing the weight parts, the mixture was poured into a tube having a diameter of 50 mmφ and a barrel length of 2.5 mm at a rate of 10 kg/hour. A blowing agent having a composition of Freon-11/Freon-22 = '50150 is supplied to a 100-degree extruder L, cross-wire melted at 230°C, and a high-pressure pump is added to the polystyrene at a ratio of 15 parts by weight to polystyrene. After the molten mixture is press-fitted into the molten resin, the molten mixture is further kneaded and the blowing agent is uniformly dispersed in the molten resin, the molten composition is cooled from the outside to 150°C at the tip of the extruder, Figure 7. It was extruded into the atmosphere through a nozzle having 22 extrusion holes with a semicircular diameter of r = l ays, and was allowed to freely foam, with a thickness of t = 8 + u and a width of W = 10 as shown in Figure 4.
A continuous semi-cylindrical foam strip with a dragon longitudinal section was obtained.

After passing the foam strip through a take-off roll while cooling in the atmosphere, it is shown in Figure 4a! = 50 am, ! +=
1/2L, cut diagonally into the shape of θ1-θ2 = 20 degrees L,
Next, the cut foam strips were introduced into a foaming furnace and heated with steam at 115° C. for 20 seconds to form a re-foamed L, a rose of the present invention having a three-dimensionally curved shape at both ends as shown in FIG. 1a and b. A shaped buffer was obtained. As a comparative example, cut foam strips were cut into small semi-cylindrical shapes perpendicular to the extrusion direction as shown in FIGS.
A comparative loose shock absorber having a non-curved shape as shown in Figures a and b was obtained. Table 1 shows the characteristic values of the bulk buffer bodies of Examples and Comparative Examples thus obtained.

Examples and comparisons were used, except that a die with 11 circular extrusion pores of 2r = 1 mm arranged as shown in Fig. 8 was used, and 8 parts by weight of butane was used as a blowing agent per 100 parts by weight of polystyrene. t2=lO obtained by operating in the same manner as Example-1
The continuous cylindrical foam strip of the proverb is shown in Figure 5a at t = 1.
0 meetings, E=501II1. Ll-15, θ=3
The cut foam strip of the example obtained by cutting at 0 degrees and the cut shown in FIG. 11 C1d obtained by cutting the extruded foam strip into small cylinders at t = 50 am perpendicular to the extrusion direction By heating the foam strips in the same manner as in Examples and Comparative Example-1, the foam strips were heated in the same manner as in Examples and Comparative Example-1 to form loose j [body and no. As shown in FIG. 11 C1d, a loose v1 impactor of a comparative example having a shape without curvature was obtained.

Table 1 shows the characteristic values of the bulk buffer material thus obtained.

A pond using a die in which 11 rectangular extrusion pores are arranged, where d = 1 angle and the four corners are circular arcs with a radius of curvature = 2, as shown in Fig. 9, was made in the same manner as in Example and Comparative Example-2. The obtained open foam strips of vertical cross section with thickness and width of t = 10 are shown in Fig. 6 and Fig. 12, as shown in c, θ, = θ.
2=22 degrees, θ嘗=θ2=11 degrees, length! =50■l
After cutting each diagonally so as to have a shape of 100 mm, and then heating it in the same manner as in Example and Comparative Example-2, a rose-like shape 111 of the present invention having a three-dimensionally curved shape at both ends as shown in FIG. 3 is obtained. As shown in FIGS. 12a and 12b, comparative loose shock absorbing bodies were obtained which had a shape that did not satisfy the characteristic values of the present invention due to little curvature.

Table 1 shows the characteristic values of the loose Ml bombs thus obtained.

As shown in Table 1, the bulk buffer exhibiting characteristic values within the limited range of the present invention has a large packing density of 160 mE/g or more, but the characteristic values within the limited range of The packing density of the foam of the comparative example that was removed was 90 m
It can be seen that the packing density is less than 1/g, which is less than 1/2 of the packing density of the bulk monolayer of the example.

Table 1 Put the loose buffer into the cardboard box Ocm until it is full, measure the buffer weight (g) of this full amount, and calculate the ratio of the contents of the cardboard box flI (Vm to (g)). m Z / g
Let be one packing density.

(Effects) As described above, the present invention is a loose shock absorber having a three-dimensionally curved shape at both ends, and is different from the conventional loose H8 body shown in the comparative example having a shape with less three-dimensional curvature. In comparison, the same buffering effect can be achieved even if the amount filled into the storage container is less than 1/2.

The conventional loose cushioning material in the shape of a curved string requires time and effort to divide the large intertwined string-like cushioning materials into smaller pieces, or when the strings are pulled to be separated into smaller pieces, the strings break and become shorter, reducing the filling effect. Since the bulk cushioning material of the present invention does not become entangled with each other, there is no need to divide it into smaller portions, and there is no fear that the filling effect will deteriorate, making it easy to handle.

In the method for manufacturing a bulk cushioning body of the present invention, a foam obtained by extruding and foaming from an extruder is diagonally cut L at a predetermined size ratio and at a predetermined angle, and is re-foamed by heating. Curved string-shaped prior art loose shape [No need for the hassle of quenching step in R-body production, less three-dimensional curvature, prior art loose M cross-shaped manufacturing method and 2 Easily produced in almost the same process This is an excellent invention that will play a large role in industry.

[Brief explanation of drawings]

Figures 1 to 9 are diagrams explaining the present invention in detail, Figures 1 to 3 are perspective views of the bulk cushioning bodies of the present invention corresponding to Examples 1 to 3, Figure 1 is a diagram illustrating Figure 1a. View from the back, Figures 4-6a
4 is a front view of an extruded foam strip cut diagonally for re-foaming to form the bulk cushion shown in FIGS. 1-3; FIG.
Figures 6 to 6 are cross-sectional views taken along the line A-A in Figures 4 to 6a, and Figures 7 to 9.
The figures are front views of the extrusion holes of the die used to obtain the extruded foam strips shown in Figures 4 to 6, and Figures 10 to 12 are comparative examples using the die holes of Figures 7 to 9. Figure 10 C1 Figure 11 C1
Figure 12 is a front view of a small piece cut vertically from the foam strip extruded from the die holes in Figures 7 to 9;
Figure 1 d, Figure 12 C is the 10th [Nc, Figure 11 C1 1st
2. Cross-sectional view taken along line A-A in Figure 2, Figure 10a, Figure 11a,
Figure 12a is a perspective view of a foam obtained by heating and re-foaming the foam strips cut into small pieces as shown in Figure 10C5 Figure 11C1 Figure 12B; Figure a, 11th
A sectional view taken along the line A-A in Figure a is shown. Y is the overall width, the length of the loose buffer, T+ is the thickness at the center, T2 is the thickness at both curved ends, W is the width of the molded body, θ5, θ2 are the cutting angles, and t is The length of the cut body, 1.1 is the horizontal length of the diagonal cut, t is the maximum thickness, W is the width of the maximum thickness, r is the diameter of the semicircle, d is the width of the square shape, r
I indicates the radius of curvature of the quadrangular arc.

Claims (3)

[Claims] (1) A thermoplastic resin foam that forms an S-shape. The ratio of length L, center wall thickness T_1, tip wall thickness T_2, molded body width W, and overall width Y is T_1/L=0.1 to 0.6, T_
1/T_2>2, W/L=0.2~0.5, Y/L=0
．． 4 to 1.5, Y/W=1.2 to 5.0, and a density of 0.005 to 0.05 g/ml. (2) The thermoplastic resin foam according to claim 1, wherein the actual dimension of L is 30 to 100 mm. (3) The molten thermoplastic resin containing a foaming agent is extruded into the atmosphere through a die with multiple pores attached to the tip of the extruder, and the resulting foam strips are cooled and diagonally in the extrusion direction. 2. The method for producing a thermoplastic resin foam according to claim 1, further comprising cutting the foam into strips, and then heating and re-foaming the cut foam strips.