JPS6037138B2 - Styrenic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and useful styrenic resin composition, and more particularly, the present invention relates to a new and useful styrenic resin composition. The present invention relates to a resin composition.

When molding styrene resin by injection molding or injection blow molding, the molded product often adheres to the mold and cannot be easily "released from the mold."

These mold release defects cause deformation and breakage of the molded product,
This results in a decrease in productivity, and also causes a large residual strain in the molded product, resulting in a decrease in the solvent resistance, impact resistance, etc. of the molded product.

Therefore, in order to eliminate such mold release defects, methods such as 1) selection of appropriate molding conditions, 2) application of rattan molding agent to the mold surface, and 3) addition of mold release agent to the resin are available. Although the problem has been proposed, methods 1) or 2) are rarely used to solve the problem, and are often used in combination with method 3).

Well-known scale-forming agents used for the sticks include higher fatty acids or their metal salts, esters or amides, key oils, silicone oils, and waxes.

However, when adding these mold release agents to the resin to improve the moldability and avoid the problem of poor mold release, it is necessary to add a large amount to impart the desired moldability. Therefore, it is not desirable from an economical point of view, and in the case of higher fatty acids, the mold surface may be contaminated by heat and decomposition products, and the decomposition products may be mixed into the molded product. Furthermore, it is not preferable because it may cause coloring of the resin, shortening of life span, discoloration, reduction in heat resistance, generation of odor, or reduction in transparency.

For these various reasons, there is a desire for a template agent that can exhibit the desired mold release effect even when added in a small amount and that also has good thermal stability. Next, we will discuss the criteria for evaluating the template property, that is, the evaluation scale for mold releasability in this type of injection molding or injection hollow molding. The problems will be the release from the core of the parison (core temperature = about 95 qo to 160 oo) and the mold release from the hollow mold of the hollow molded product (mold temperature = about 60 qo or less).

In other words, to actually obtain a hollow molded product using the injection blow molding method, first the synthetic resin is heat-plasticized and injection molded to form a bottomed parison, and then the molten parison is held in the core. The mold is then transferred to a hollow mold for blow molding, and air is blown into it to form the mold. If it is too low, it will be difficult to mold the resin from the core, and if it is too high, the surface of the resulting hollow molded product will be wrinkled, which is undesirable. Therefore, the wider the temperature range (core temperature range) from the upper limit core temperature that does not cause wrinkles on the surface of the hollow molded product to the lower limit core temperature that allows the molding of resin from the core, the better the workability. Moreover, it can be evaluated as having excellent mold releasability.

Next, the release of the hollow molded product from the hollow mold corresponds to the release of the molded product from the injection mold in the injection molding method, but in the former case, the hollow molded product is not processed. The releasability can be evaluated from the state of falling when pushed out with compressed air.

In particular, it is generally easy to judge when a large number of small containers are molded; in cases of good template quality, all the molded products fall into the receiving box at the same time in a striped parabola; If the molded product has poor mold release properties, the molded product will not fall smoothly; in some cases, the molded product will fall in pieces, and in other cases, it will fly out far away. On the other hand, the mold releasability in the case of the latter injection molding method is determined by the falling ball impact strength of the injection molded product, which is thought to have a large influence on the size of the scale-like property due to residual strain, and the impact strength of the molded product at the time of mold release. It can be evaluated based on the cumulative number of cracks that occur.

It should be noted that resin compositions that allow easy release of the bottomed parison from the core, which is particularly important in the injection blow molding method, generally exhibit excellent moldability in the injection molding method.
This has been discovered by the present inventors. By the way, as a mold release agent used in resin compositions for injection blow molding, a combination of mineral oil and a metal salt or amide of a higher fatty acid has been described in Japanese Patent Publication No. 1236/1983, and a combination of a saturated linear carboxylic acid The combination of and metal salts of higher fatty acids was disclosed in JP-A-52-11.
No. 27454 discloses a combination of a higher fatty acid and/or a metal salt of a higher fatty acid and polyoxypropylene glycol, and Tokoseki No. 55-34203 discloses a combination of a higher fatty acid and/or a metal salt of a higher fatty acid and a glycerin monostearate. The combination with Tokuseki Sho 54-113265
They are disclosed in the respective publications.

However, as long as conventional scale-forming agents including these are used, a total amount of 0.5 weight is required to ensure sufficient mold release properties, not only when used alone but also when used in various combinations. % or more, and there are disadvantages in terms of economic efficiency.On the other hand, even if it is sufficient to use a small amount, there are problems with workability, especially at the start of the molding process. When fatty acids are used alone or in combination with other substances, their oily thermal decomposition products may get mixed into the molded product or adhere to the core during long-term continuous operation of the molding machine. There are various disadvantages such as yellowing or coloring of the resin and shortening of the resin life. On the other hand, when metal salts of higher fatty acids are used, there are also drawbacks such as the transparency of the molded product being impaired and a striped pattern appearing on the surface of the molded product. However, in view of the above-mentioned actual situation, the present inventors have earnestly studied the combination of such effective mold release agents in order to find the most effective mold release agent. The present invention was completed by discovering that a remarkable mold release effect can only be expressed by combining carboxylic acid esters that do not exhibit the above properties with metal salts or amides of higher fatty acids. .

That is, the present invention uses styrene resin, esters of carboxylic acids and monovalent or divalent saturated aliphatic alcohols, and metal salts or amides of higher fatty acids as essential components. For each type of styrene-based resin, one or more of the above ester-type songs are 0.
．． 0.01 to 1% by weight, and one or more of the above metal salts or amides {C}
The object of the present invention is to provide a styrenic resin composition which is added in an amount of 1% by weight, has particularly excellent mold releasability, and can be subjected to injection molding or injection blow molding. By the way, polystyrene with excellent impact resistance and a rubber content of about 5% by weight or more (hereinafter, these are abbreviated as HI polystyrene).

) has a tendency to reduce the amount of rubber in order to improve economy, surface gloss, hardness, etc. However, polystyrene with a rubber amount of about 2 to 4% by weight obtained in this way is not popular in the market. "Medium Impact Polystyrene" (hereinafter abbreviated as MI polystyrene). In the past, even with HI polystyrene, mold releasability did not pose much of a problem simply by adding mineral oil, but with MI polystyrene, the reduction in rubber content made it difficult to mold, making molding difficult. Because large residual strains occur in the product and reduce the strength of the molded product, it is absolutely necessary to add a template agent, and in many cases, such template agents such as stearic acid or calcium stearate are used. Higher fatty acids or their metal salts have been used by themselves or in various combinations, such as M
For resins such as I-polystyrene that do not have good template properties, it is difficult to select a template agent, and the current situation is that a sufficient mold release effect cannot be obtained using conventional mold release agents and combinations.

However, according to the present invention, it is possible to obtain a resin composition that has extremely superior mold releasability and high impact strength compared to conventional MI polystyrene. In the present invention, the above-mentioned styrenic resin wind uses at least one monomer selected from the respective groups of styrenic monomers and other pinyl monomers copolymerizable with the monomers, Furthermore, if necessary, it refers to those obtained by polymerizing in the presence of a rubber-like substance, but among them,
First, styrenic monomers include styrene, Q-methylstyrene, and benzene nuclei whose hydrogen atoms are halogen atoms and carbon atoms.
, ~C4 is a general term for styrene derivatives substituted with alkyl groups, and representative examples of such styrenic monomers include styrene, o-chlorostyrene, p-chlorostyrene, p-methylstyrene, 2
, 4-dimethylstyrene or t-butylstyrene.

In addition, typical copolymerizable vinyl monomers include acrylonitrile monomers such as (meth)acrylonitrile, Q-chloroacrylonitrile, or pinylidene cyanide; (meth)acrylic acid, (meth)acrylic acid, and ) Methyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, glycidyl (meth)acrylate, 2-ethylhexyl (meth)acrylate or (
(meth)acrylic acid and its various esters such as 8-hydroxyethyl meth)acrylate; or vinyl acetate, vinyl chloride, vinylidene chloride, vinylpyrrolidone, (meth)acrylamide, dimethyl (meth)acrylamide, maleic anhydride These include acids, itaconic anhydride or maleimide, as well as vinyl ketones or vinyl ethers.

Furthermore, typical rubber-like substances mentioned above include polybutadiene rubber, styrene-butadiene copolymer rubber, styrene-butadiene-styrene flock copolymer rubber, ethylene-propylene terpolymer rubber, and butadiene-acrylonitrile copolymer rubber. Rubber, butyl rubber, acrylic rubber, styrene/isobutylene/butadiene copolymer rubber, or isoprene/acrylate ester copolymer rubber, etc. obtained using conjugated 1,3-gene monomers such as isoprene or chloroprene. There are rubber, etc., and these can be used singly or in combination of two or more.

On the other hand, the above-mentioned metal salts of higher fatty acids refer to salts of higher fatty acids with metals such as IJ tium, sodium, potassium, magnesium, calcium, aluminum or zinc, and the higher fatty acids are C, 2-
It is a general term for linear saturated monocarboxylic acids of C32, and representative examples of such higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and montanic acid. be.

Representative examples of metal salts of higher fatty acids include magnesium stearate, aluminum stearate, calcium stearate, and zinc stearate. Representative examples of the above-mentioned amides of higher fatty acids include stearamide, methylene pistearamide, ethylene bis stearamide, oleylamide, and oxystearic acid ethylene diamide.

Furthermore, the above-mentioned carboxylic acid esters 'B} are
In particular, it collectively refers to the various higher fatty acids listed above, as well as saturated aliphatic mono- or dicarboxylic acids such as phthalic acid, adipic acid, tartaric acid, citric acid or sebacic acid, and aromatic dicarboxylic acids or oxycarboxylic acids. It refers to esters of carboxylic acids and monovalent or divalent saturated aliphatic alcohols, and representative examples of such esters of carboxylic acids include stearyl stearate, stearyl palmitate, and n-tartrate.
Butyl, <triethyl citrate, di- or tristearyl citrate, di-i-butyl adipate, di-2-ethylhexyl adipate, di-n-butyl sebacate,
Examples include di-n-octyl sebacate, ethanediolmontanate, 1,3-butanediolmontanate, di-n-octyl phthalate, di-i-octyl phthalate, and di-2-ethylhexyl phthalate.

Among these, esters with low boiling points are easily released during molding, so they may adhere to molds, etc., or the volatile substances of these esters may be further oxidized and degraded, contaminating the molded product. In addition, it also reduces the heat resistance of the resin itself, so gesters of dihydric alcohols and higher fatty acids and gesters of higher alcohols and dibasic acids are particularly preferred.

The above-mentioned styrene resin, carboxylic acid ester [B', and metal salts or amides of higher fatty acids] are used as essential components, and these components are uniformly mixed. Conventional means such as extruders, heated rolls or Banbury mixers can be used to effect the mixing.

In such a case, there is no hindrance to adding the {B} and/or {q component in advance at the stage of preparing the styrene resin (2), and uniform mixing can also be achieved by such a method. I can do it.
The thus obtained composition of the present invention can also contain various additives commonly used in styrenic resins of this type, including key oil, and the amount of the additives to be added may also vary from the conventional amount. Of course, it may be.

The composition of the present invention can improve the walking speed in injection blow molding, and can also reduce residual strain in injection molding, and can provide molded products with high impact strength.

The most noteworthy effect of the composition of the present invention is that it has excellent mold release properties. Since the releasability of the resin can be obtained, it is excellent in economical efficiency, and the accompanying effect of less deterioration of the physical properties of the resin itself can be expected.

Furthermore, by using the composition of the present invention, no deposits are formed on the core even during long-term continuous operation for as long as one month, and a good mold release effect can be maintained over a wide molding temperature range. Effects such as being able to do this are brought about.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples, where all parts and percentages are based on weight unless otherwise specified. Examples 1 to 4 and Comparative Example 1 to
9 5 parts each of "Dick Styrene CR-3500" [GP polystyrene manufactured by Dainippon Ink & Chemicals Co., Ltd.] and 5 parts each of "Dick Styrene GH-6300" [Machi polystyrene manufactured by the same company] and Table 1. Predetermined amounts of various additives as shown were uniformly melt-mixed using an extruder to form respective pellets.

Next, each of the various pellets was individually molded into a container having a weight of 62 mm and an internal capacity of 100 mm using an injection blow molding machine.

The core temperature range within which a good molded product could be obtained was investigated by varying the core temperature.

In addition, to determine the roughness of molded products from hollow molds, we investigated the percentage of molded products that did not fall normally and flew out when each molded product was ejected by pressurized air and separated from the mold. It was evaluated based on the following.

The results are summarized in Table 1.

As can be seen from the results shown in the same table, the composition of the present invention requires the addition of an extremely small amount of mold release agent compared to the comparative product, and can be molded into good quality products over a wide core temperature range. It is already clear that the composition of the invention has excellent neighborhood properties.

In Table 1 * "Core Temperature Range", the numbers in the upper row indicate the temperature range itself and the lower limit.

Examples 5 to 8 and Comparative Examples 10 to 13 In an autoclave with a pseudo-clothing layer, 4 parts of "Gen NF35" [polybutadiene rubber manufactured by Asahi Kasei Kogyo Powder] per 10 parts of styrene monomer. Then, 0.05 part of t-dodecyl mercaptan was added thereto, and the solution was then heated to 100°C at a rate of 1°C/2 minutes to carry out prepolymerization.

After that, when the temperature was maintained at the same temperature and phase transition occurred, 13 parts of water was added to 10 parts of the obtained prepolymerization liquid, and then 2 parts of water was added as a suspension stabilizer. gocalcium phosphate,
0.3 parts of partially saponified polyvinyl alcohol and 0.3 parts of partially saponified polyvinyl alcohol.
Add 0.03 parts of sodium dodecylbenzesosulfonate, then sequentially add 0.5 parts of penzoyl peroxide and 0.05 parts of dicumyl peroxide, purify the system with nitrogen gas, and then heat at 9000 for 8 hours. Suspension polymerization was carried out, and further 130
The polymerization reaction was continued for 2 hours at a temperature of 0.00°C, and then the reaction was completed.

Thereafter, the resulting granular resin was thoroughly washed, dehydrated, and then dried.

Thereafter, the process was carried out in the same manner as Examples 1 to 4 and Comparative Examples 1 to 9, except that the predetermined amounts of various additives shown in Table 2 were used for each 10 parts of this granular resin. Injection hollow molding was performed, and then templateability was evaluated.

The results are summarized in the same table.

Table 2 *As mentioned above in Table 1.

Examples 9 and 10 and Comparative Examples 14 to 19 “Dietz Styrene CR-3500” and “Dietz Styrene GH-9100” [HI polystyrene manufactured by the same company]
Five anchorages of each of the above and predetermined amounts of various additives as shown in Table 3 were uniformly melted and mixed using an extruder to form each pellet.

Next, each of the various pellets was individually molded using an injection molding machine at a molding temperature of 25°C and a mold temperature of 60°C to form a lid-shaped molded product with a wall thickness of 205 x 125 x 22 mm on the second side. Obtained.

Thereafter, the falling ball impact strength of each of these molded products was examined using a steel ball weighing lk9 and having a diameter of 32 ribs.

The results are summarized in the same table.

Examples 11 and 12 and Comparative Examples 20 to 24 Ten anchors of "Dix Styrene CR-3510" (GP polystyrene manufactured by the same company) and predetermined amounts of various additives shown in Table 4 were uniformly mixed using an extruder. The pellets were melted and mixed to obtain various pellets.

Next, each pellet was individually molded into various lids using an injection molding machine in the same manner as in Examples 9 and 10 and Comparative Examples 14 to 19, except that the molding temperature was 190°C and the mold temperature was 60°C. A molded product was obtained.

The cumulative value of the number of cracks in a single solid molded product obtained in a steady state was used as a data for the patternability of the resin. The results are summarized in the same table.

Table 3 Table 4 Examples 13 to 15 and Comparative Examples 25 to 29 In a polymerization kettle with an internal capacity of 5, 150 liters of water was added to 60 qo, and 4.5 parts of carboxymethyl cellulose and polyacrylic 4.5 parts of sodium chloride and 0.045 parts of polyvinyl alcohol were added and dissolved for 3 minutes, and 1275 parts of styrene monomer, 225 parts of methacrylic acid and 2.3 parts of penzoyl peroxide were added thereto. Polymerization was carried out at 8 oz for 6 hours and then at 130 qo for 3 hours.

Next, the pearl-like styrene/methacrylic acid copolymer thus obtained and predetermined amounts of various additives shown in Table 5 were uniformly melt-mixed using an extruder to obtain various pellets.

Thereafter, each pellet was individually molded into various lids using an injection molding machine in the same manner as in Examples 9 and 10 and Comparative Examples 14 to 19, except that the molding temperature was 280°C and the mold temperature was 80oo. A molded product was obtained.

The cumulative number of cracks in the solid molded product obtained in a steady state was used as a measure of the mold releasability of the resin.
The results are summarized in the same table.

Table 5

Claims (1)

[Scope of Claims] 1. As essential components: (A) styrene resin, (B) esters of carboxylic acids and monovalent or divalent saturated aliphatic alcohols, and (C) metal salts of higher fatty acids. or amide, and 0.01 to 1% by weight of one or more of the esters (B) based on the styrene resin (A), respectively;
and 0.01 to 1% by weight of one or more of the above-mentioned metal salts or amides (C), which has particularly excellent mold releasability and is suitable for injection molding or injection blow molding. Styrenic resin composition.