JPH0755509B2 - Vinyl chloride resin composition for injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a vinyl chloride resin composition for injection molding,
More specifically, the present invention relates to a vinyl chloride resin composition for injection molding, which is suitable as an injection molding material for shoe soles of injection molded shoes.

[Conventional technology]

In recent years, there has been a demand for weight reduction of shoes, and in order to meet this demand, in injection molding shoes, for example, as a molding material for shoe soles, a vinyl chloride (co) polymer and a plasticizer, A method for producing a lightweight shoe having a foamed sole by injection molding using a vinyl chloride resin composition mainly containing a stabilizer, a pigment and a foaming agent has come to be widely used.

This method will be described in more detail. For example, as shown in FIG. 1, in a split type last A composed of a last main body 1 and a heel portion 2,
A cover 5 to which a bottom cloth 4 having a plurality of through holes 3 is sewn is suspended and mounted to form an insole molding gap 6, and then this last A is used for the side molds 7, 7'and the bottom mold 8 By fitting and setting in the shoe sole molding gap 9 formed by the above, the midsole molding gap 6 and the shoe sole molding gap 9 are communicated with each other through the through hole 3 of the bottom cloth 4.

Here, the side molds 7 and 7 ′ are formed with an injection hole 10 for the shoe sole molding material, and the shoe sole molding material is injected and filled from this injection hole 10. The shoe sole molding material injected and filled through the injection hole 10 flows into the insole molding void 6 through the shoe sole molding void 9 and the plurality of through holes 3 formed in the sole cloth 4 without any gap, and A shoe molded integrally with is manufactured. At this time, since the foaming agent is contained in the sole molding material injected through the injection hole 10 as described above, the foaming agent is thermally decomposed at the time of melting and injected through the injection hole 10, so that the sole molding void is formed. 9
Further, a lightweight shoe is obtained in which the upper and lower layers of the shoe sole are skinned by foaming in the inner sole molding void 6, and the inside is finely foamed (core).

[Problems to be solved by the invention]

By the way, the foaming agent used as a conventional injection molding material is usually nitrogen gas or water (water vapor) during thermal decomposition.
The molding material injected from the injection hole 10 forms a gas flow along the melting flow, and so-called "flow scratches" with a wood grain are formed on the bottom surface of the shoe sole, the side surface of the shoe sole, etc. Was spoiling. In addition, when manufacturing injection-molded shoes using such injection-molding materials, the bolts that fix the side molds, etc. to generate water from the foaming agent may corrode, causing mold corrosion. There was found.

The present invention has been made against the background of such a technical problem. When manufacturing an injection-molded article such as an injection-molded shoe, flow soles are not generated on the sole, and corrosion of the injection-molding die is caused. It is an object of the present invention to provide a vinyl chloride resin for injection molding.

[Means for solving problems]

That is, the present invention is based on 100 parts by weight of a vinyl chloride (co) polymer, 60 to 120 parts by weight of a plasticizer, 1 to 5 parts by weight of a pigment, 0.5 to 1.5 parts by weight of a foaming agent, and 0.5 to 1.5 parts of calcium oxide.
The present invention provides a vinyl chloride resin composition for injection molding, which contains 5 parts by weight.

The vinyl chloride (co) polymer used in the present invention means a vinyl chloride homopolymer having vinyl chloride as a repeating structural unit, or ethylene-copolymerized with ethylene as a main repeating structural unit of vinyl chloride. In the case of a vinyl chloride copolymer, the ethylene content (repeating structural unit of ethylene) in the case of the copolymer is usually 0.5 to 5% by weight, preferably 1 to 3% by weight, and exceeds 5% by weight. The ratio of ethylene, which is a copolymerization component, increases, making it difficult to produce a copolymer, and the melt viscosity during injection molding becomes too low, or sink marks occur in the molded product, and thermal decomposition occurs during molding. It is not preferable to do so.

The average degree of polymerization of this vinyl chloride homopolymer is preferably
1,050-1,450, more preferably 1,050-1,300,
If it is less than 1,050, the polymerization degree is too low and the injection moldability is excellent, but after molding, physical properties such as abrasion resistance, compression molding strain, and shape retention at high temperature are poor, while if it exceeds 1,450, the polymerization degree is too high and injection is performed. The injection moldability such as a defect may be poor, or the injection molding distortion may be large and the molded product (for example, the sole) may shrink even after molding.

In the case of ethylene-vinyl chloride copolymer, its average degree of polymerization is preferably 1,050 to 1,700, more preferably 1,050 to 1,300 for the same reason.

The vinyl chloride resin composition for injection molding of the present invention is a composition in which the vinyl chloride (co) polymer contains a plasticizer, a pigment blowing agent, calcium oxide, and, if necessary, a stabilizer.

Examples of the plasticizer include phthalic acid esters such as dibutyl phthalate, dioctyl phthalate and butylbenzyl phthalate; aliphatic polybasic acid esters such as dioctyl adipate, dioctyl azelate and dioctyl sebacate; phosphoric acid esters such as tricresyl phosphate. A citrate ester, an epoxy-based plasticizer, a polyester-based plasticizer, a urethane-based plasticizer, and the like, and a phthalic acid ester is preferable.

The amount of the plasticizer used is 60 to 120 parts by weight, preferably 60 to 80 parts by weight, based on 100 parts by weight of the vinyl chloride (co) polymer, and if it is less than 60 parts by weight, phenomena such as poor injection may occur. ,
On the other hand, if it exceeds 120 parts by weight, physical properties such as abrasion resistance, compression molding strain, adhesiveness, and shape retention at high temperature may be deteriorated.

As the pigment, for example, phthalocyanine green,
Examples include chrome yellow, titanium oxide, carbon black, and the like. These pigments are appropriately selected depending on the injection-molded article to be obtained such as shoe soles. The amount of this pigment used is 100 parts by weight of vinyl chloride (co) polymer,
1 to 5 parts by weight, preferably 3 to 4 parts by weight. When the amount is less than 1 part by weight, the resulting injection-molded product has poor coloring effect, and the pigment tends to cause non-uniform dispersion. Even if flow flaws due to nitrogen gas generated from the foaming agent are still conspicuous, the coloring effect does not increase proportionally even if the amount exceeds 5 parts by weight, and the flow scratch prevention effect does not increase proportionally, which is uneconomical. Is.

Further, the foaming agent used in the present invention is a decomposition-type foaming agent that decomposes by heat to generate at least water. Specific examples of this foaming agent include sodium bicarbonate (decomposition temperature 90 ° C., generation temperature). Inorganic blowing agents such as gas; carbon dioxide and water), ammonium bicarbonate (decomposition temperature 35-60 ° C, evolved gas; ammonia, carbon dioxide and water); p-toluenesulfonyl hydrazide (TSH, decomposition temperature 1
05-115 ° C, evolved gas: nitrogen and water), p, p'-oxy-bis (benzenesulfonylhydrazide) (OBSH, decomposition temperature 150-160 ° C, evolved gas: nitrogen and water), benzenesulfonylhydrazide (BSH, An organic foaming agent represented by a hydrazide-based foaming agent such as a decomposition temperature of 100 to 120 ° C., a generated gas; nitrogen and water) can be mentioned. Of these foaming agents, organic foaming agents having a sharp decomposition temperature and a short decomposition time are preferable, and p, p'-oxy-bis (benzenesulfonylhydrazide) (OBSH) is more preferable. The amount of the foaming agent used is 0.5 to 1.5 parts by weight, preferably 100 parts by weight of the vinyl chloride-based (co) polymer.
0.8 to 1.2 parts by weight, less than 0.5 parts by weight has poor foaming effect, while more than 1.5 parts by weight causes excessive foaming, resulting in deterioration of physical properties such as injection molded shoes such as strength and wear resistance. In addition, the effect of preventing flow scratches may not be sufficiently exerted even by adding calcium oxide described later.

The composition of the present invention further contains calcium oxide as an essential component. This calcium oxide is removed from a molded product that can generate water by reacting with the generated water to generate calcium hydroxide when the foaming agent decomposes to generate water (that is, steam). It acts to do. The amount of calcium oxide used is 0.5 to 100 parts by weight of the vinyl chloride (co) polymer.
It is 5 parts by weight, preferably 1 to 3 parts by weight, and if it is less than 0.5 parts by weight, the effect of removing water is poor, flow scratches due to generated gas are conspicuous, and it is difficult to prevent corrosion of the injection molding die. Even if the amount exceeds 5 parts by weight, the moisture removing effect does not increase proportionally, and in some cases, the physical properties of the obtained molded product may not be within the desired range due to too much calcium oxide content, and the color tone is poor. There are cases.

The average particle size of the calcium oxide used in the composition of the present invention is 1.0 to 10 μm, preferably 1.5 to 5 μm.
If it is less than 1.0 μm, not only is it too fine to increase the manufacturing cost, but it also has a problem that it absorbs moisture during storage because it has a large surface area. It is not preferable because the surface of the shoe sole becomes rough.

The composition of the present invention may further contain a stabilizer if necessary. Examples of this stabilizer include tin-based stabilizers such as dibutyltin laurate and metal soaps such as zinc stearate and calcium stearate.

The amount of this stabilizer used is 100% vinyl chloride (co) weight.
1 to 4 parts by weight, preferably 2 to 3 parts by weight, relative to 1 part by weight, less than 1 part by weight has poor thermal stability and may cause thermal decomposition during molding, while more than 4 parts by weight. Even if it is used, the effect of using the stabilizer is not proportionally improved and it is uneconomical.

The vinyl chloride resin composition for injection molding of the present invention can be used as it is, but it is used by blending other thermoplastic resin, rubber, filler, lubricant, etc., if necessary,
The specific gravity of the obtained molded product is usually about 0.85 to 0.90.

As the other thermoplastic resin, for example, ABS resin, chlorinated polyethylene, ethylene-vinyl acetate copolymer, urethane, acrylic resin and the like, as the rubber, acrylonitrile-butadiene rubber is used, the content of these,
Usually, 30 parts by weight or less is used with respect to 100 parts by weight of the ethylene-vinyl chloride (co) polymer of the present invention.

As the filler, for example, calcium carbonate, talc, titanium oxide, aluminum hydroxide, magnesium hydroxide, clay, magnesium carbonate or the like is used in an appropriate amount, if necessary.

Furthermore, as the lubricant, for example, a lubricant such as a higher fatty acid ester or a low molecular weight polyethylene which is usually used in a vinyl chloride resin composition is used.

The vinyl chloride resin composition for injection molding of the present invention is mixed and mixed in the same manner as a conventional vinyl chloride resin composition and used as an injection molding material.

That is, using a mixer such as a super mixer or a blender, a vinyl chloride (co) polymer, a plasticizer, a pigment, a foaming agent, calcium oxide, a stabilizer, and if necessary, other thermoplastic resin, rubber, a filler, Lubricants and the like are mixed, mixed with a Banbury mixer, a mixing roll, an extruder and the like, further granulated as necessary, and used as an injection molding material.

The vinyl chloride resin composition for injection molding of the present invention is used in various fields for injection molding, such as packing, tubes,
It can be used for hoses, leather, wire coatings, bellows shaped products, automobile bumpers, bicycle handle grips, base materials for electronic devices, etc., but also for the soles of injection-molded shoes or injection-molded boots described above. In particular, it has a particularly remarkable effect.

[Action]

The foaming agent present in the resin composition of the present invention is thermally decomposed at the time of injection molding to generate water vapor, nitrogen gas and the like. The generated water vapor is combined with calcium oxide present in the composition to generate water. It becomes calcium oxide and prevents the occurrence of so-called flow scratches in wood grain due to gas flow. Nitrogen gas and the like generated at the same time can be made inconspicuous by increasing the pigment content. Also,
As a result of trapping the generated steam, corrosion of the injection molding die does not occur. Furthermore, calcium oxide is changed into calcium hydroxide by steam, and also functions as a filler in the resulting molded article.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Examples 1-2 and Comparative Examples 1-6 Injection-molded shoes were manufactured using the apparatus shown in FIG.

At this time, the composition of the sole of the injection-molded shoe was the composition shown in Table 1, and the molding temperature and injection pressure were 198 ° C and 30 kg / cm.
It was ² · G.

The results are also shown in Table 1.

In Table 1, the flow flaw is a visual observation of a state in which the generated gas flows along the flow of the injection molding material at the side of the shoe sole during the injection molding and the woodgrain-like flow flaw remains. The term "die corrosion" means that the presence or absence of corrosion is determined by observing the bolts that fix the side mold after injection molding 20 times using this die.

* 1) Vinyl chloride homopolymer with an average degree of polymerization of 1,300 * 2) Dioctyl phthalate * 3) Special colorant; 006 black * 4) p, p'-oxy-bis (benzenesulfonylhydrazide) * 5) Average particle size About 2.5 μm * 6) Dibutyltin laurate As is apparent from Table 1, the resin composition of the present invention does not cause flow scratches and mold corrosion, and a shoe sole having a low specific gravity can be obtained. On the other hand, in the case where calcium oxide is not included, flow scratches are generated due to the generated steam, and there is mold corrosion (Comparative Example 1). When calcium oxide is too much, flow scratches and mold corrosion do not occur. , The specific gravity increases,
The jet blackness of the appearance is impaired (Comparative Example 2), and if the foaming agent is too small, flow scratches and mold corrosion are not so noticeable, but the specific gravity becomes heavy and it does not lead to weight reduction (Comparative Example 3). If the amount of the agent is too large, not only the effect of adding calcium oxide cannot be exhibited, but also the foamed cell structure becomes coarse and the performance as a shoe is not satisfied (Comparative Example 4). Pyrolysis easily occurs,
Therefore, injection failure occurs (Comparative Example 5), and when the amount of the plasticizer is too large, not only the shoe is too soft, but also the plasticizer may bleed on the surface of the shoe (Comparative Example 6).

〔The invention's effect〕

As described above, the composition of the present invention is capable of instantaneously capturing moisture generated by thermal decomposition from a foaming agent during injection molding with calcium oxide and preventing wood grain flow scratches due to gas flow (water vapor). It is also possible to prevent corrosion of the injection mold.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an apparatus for producing an injection-molded shoe using the resin composition for injection molding of the present invention.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C08K 5/10 KGY 5/24 GHH C08L 27/06 KGG // B29K 27:06 105: 04 505: 00

Claims (1)

[Claims] 1. A plasticizer 60 to 120 parts by weight, a pigment 1 to 5 parts by weight, and a foaming agent to 100 parts by weight of a vinyl chloride (co) polymer.
A vinyl chloride resin composition for injection molding, which comprises 0.5 to 1.5 parts by weight and 0.5 to 5 parts by weight of calcium oxide.