JPS62132951A - Styrene based resin composition - Google Patents

Abstract

PURPOSE:A composition, obtained by blending a specific rubber-modified polystyrene based resin or a mixture thereof with transparent polystyrene based resin with a higher fatty acid and metal salt thereof, having remarkably improved mold releasability, uneven wall thickness and stiffness and capable of preventing the occurrence of black spots. CONSTITUTION:A styrene based resin composition obtained by blending (A) 100pts.wt. rubber-modified polystyrene based resin or a mixture thereof with a transparent plystyrene based resin unmodified with rubber having 2.0-4.5wt% rubber concentration (Cr), 1.0-4.5mum rubber volume average particle size (dv) and within 4-18 range of dvXCr value with (B) 0.1-0.4pts.wt. each two or more >=4C higher fatty acids in 0.3-0.8pts.wt. total amount thereof and (C) 0.05-0.15pts.wt. one or more metal salts of higher fatty acids. Stearic acid, etc., may be used as the component (B) and calcium stearate, etc., as the component (C).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a styrenic resin composition suitable for injection blow molding.

(Prior Art) It is known to improve mold release properties during molding by adding higher fatty acids or metal salts of higher fatty acids to styrene resins. In injection blow molding, the use of higher fatty acids and their metal salts is said to be effective in releasing the mold at high temperatures. (% Publication No. 47-37493, Japanese Patent Publication No. 57-42654) The defect phenomenon of uneven thickness due to mold release failure is not the only problem, but injection blow molding can improve the stiffness of the molded product and make the molded product less opaque. This is an important issue.

For example, if a hollow molded product such as a lactic acid bacteria beverage container lacks stiffness, it can easily become damaged due to the load in the tank when it is transported from the molding process to the filling process or when the molded product is stored. Containers with low stiffness are not preferred because they become deformed and tend to cause problems during the filling process.

Furthermore, in the case of the above-mentioned lactic acid bacteria beverage containers, etc., the product name is usually printed on the outer surface of the container, but if the container is too transparent, the printing will not stand out and the contents will be too visible, making it look cheap.

Therefore, it is necessary to increase the opacity of the container as much as possible.

In addition, when injection blow molding is not carried out continuously for 24 hours, molding is interrupted, and then heat-wrapped and molding is started, resin that remains in the molding machine cylinder and heat deteriorates, causing black spots in the molded product. There is also a molding defect phenomenon called black spots caused by dust.

(Means for solving the problems) As a result of intensive research to solve the above problems of improving mold releasability, improving uneven thickness, improving waist strength, and preventing sunspots, we found that the average volume of rubber The particle size (dv) is 1.0 to 45 μm, the rubber concentration (Cr) is 2.0 to 4.5% by weight, and dvX
By using a resin mixture made by mixing and homogenizing a rubber-modified polystyrene resin or a rubber-modified polystyrene resin and a transparent polystyrene resin that is not modified with rubber, the stiffness and moldability of the molded product can be improved. The opacity of the product is improved, and by adding specific amounts of two or more types of higher fatty acids with different carbon numbers of 4 or more and one or more types of metal salts of higher fatty acids to this resin or resin mixture, injection blow molding is improved. Problematic uneven thickness,
The present invention was achieved by finding scales to improve molding defects such as poor mold release and black spots.

That is, in the present invention, the rubber concentration (Cr) in the resin mixture obtained by mixing and homogenizing a rubber-modified polystyrene resin or a rubber-modified polystyrene resin and a transparent polystyrene resin that is not modified with rubber is 2.0 to 4. 5% by weight, and the volume average rubber particle diameter (dv) of the rubber is 1.0 to 4.5 μm.
and the value of dvXCr is within the range of 4 to 18, and 0.1 to 0.1 to 0.2 or more of two or more types of higher fatty acids each having a different carbon number of 4 or more per 100 parts by weight of the resin or resin mixture.
0.4 parts by weight, 0.3 to 0.8 parts by weight as a total amount,
The present invention provides a styrene resin composition containing 0.05 to 0.15 parts by weight of one or more higher fatty acid metal salts.

For example, in injection hollow molded products, the volume average rubber particle diameter (dv
) is 1.0 to 4.5 μm and the rubber concentration (Cr) is 2.0.
~4.5% by weight, and d v X Cr = 4~
Resins in the range of 18 are suitable.

When the volume average rubber particle size (dv) is less than 1.0 μm, or when the rubber concentration (Cr) is less than 2.0% by weight, or when the volume average rubber particle size (dv) is 1.0 to 4. 5
ttm and the rubber concentration (Cr) is 2.0 to 4.5% by weight, but when dvXCr is less than 4, various disadvantages occur. Specifically, first, the molded product lacks opacity, so when printing on the outer surface of the molded product, the printing does not stand out. Second, because the molded product has low stiffness, it easily breaks when compressive force is applied to the molded product, such as when printing, air transporting, or storing the molded product.

In addition, if the volume average rubber particle diameter (dv) exceeds 4.5 μm or if the rubber concentration (Cr) exceeds 4.5% by weight, the average rubber particle diameter (dv) at a certain degree Celsius is 41,0 to 4. 5
μm, and the rubber concentration (Cr) is .

2.0 to 4.5% by weight, but when dvXCr exceeds 18, various disadvantages occur.

To explain specifically, firstly, the molded product becomes softer.
It is easily deformed by external forces. Secondly, the fluidity of the resin becomes low and the moldability deteriorates, making it more likely that defects such as uneven thickness will occur.

In other words, the volume average rubber particle diameter (dv) and the rubber concentration (Cr
) is within the range described in the claims, a resin composition with a well-balanced opacity, stiffness of the molded product, and moldability can be obtained.

The present invention is characterized by volume average rubber particle diameter (dv), rubber concentration (Cr
), but also the combination of both, dvX
It has been discovered that resins with Cr in the range of 4.0 to 18 have excellent opacity and stiffness, and this is of great industrial benefit.

In order to mix and homogenize the rubber-modified polystyrene resin and the transparent polystyrene resin that is not modified with rubber, it is preferable to mix the rubber-modified polystyrene resin and the rubber with a blurr, etc., and then knead with an extruder, etc. The resin to be mixed directly may be put into the hopper of the molding machine, and the present invention is not limited to the method of adjusting the resin.

The rubber-modified polystyrene resin used in the present invention is produced by dissolving a predetermined amount of synthetic rubber in a vinyl aromatic compound monomer or a mixture containing this monomer as a main component and a vinyl compound monomer copolymerizable with it. It refers to products produced by a method of polymerizing monomers. Preferred examples of vinyl aromatic compound monomers include styrene, P-methylstyrene,
Examples of vinyl compound monomers that can be copolymerized with P-tert-butylstyrene and α-methylstyrene include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and esters thereof. It will be done. As synthetic rubber, polybutadiene and butadiene are used at 50]
Examples include random or block copolymers of butadiene and other copolymerizable monomers containing iJi% or more. Monomers that can be used for copolymerization with butanoene include vinyl aromatic compounds such as styrene and α-methylstyrene; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; and their esters; and vinyl cyanide compounds such as methacrylonitrile. In addition to these synthetic rubbers, Po! J (soflen, polychlorogrene, terpolymer of ethylene-propylene-diene monomer, etc.) can also be mentioned.

In addition, the transparent polystyrene resins that are not modified with rubber used in the present invention include styrene, P-methylstyrene, P-methylstyrene, and P-methylstyrene.
- By polymerizing aromatic vinyl compounds such as tertiary-butylstyrene and α-methylstyrene, or by using these aromatic vinylated compounds as a product, vinyl compounds that can be copolymerized with this, such as acrylic acid and methacrylic acid. It is preferable that the ratio is the same as the ratio of components other than the rubber component of the ren-based resin, such as acid.゛Next, mixing of rubber-modified polystyrene resin and transparent polystyrene resin that is not modified with rubber also causes problems not only in the opacity and stiffness of the molded product, but also in uneven thickness due to poor mold release, clogging in the mold, and molding. In order to improve the defective phenomenon of black spots caused by interruption and restart, two types of higher fatty acids with different carbon numbers of 4 or more were added to 100 parts by weight of polystyrene, V8 resin, or resin mixture with the volume average rubber particle size and rubber concentration described above. Add 0.3 to 0.8 parts by weight of each of the above in a total amount in the range of 0.1 to 0.4 parts by weight, and further add one or more metal salts of higher fatty acids to 0.605 to 0.1 parts by weight.
It was found that adding 5 parts was effective.

When the difference in the number of carbon atoms between the two higher fatty acids is 3 or less, there is no difference in effectiveness compared to when one type of higher fatty acid is added, and there is little improvement effect on mold clogging, uneven thickness, and black spot formation. Further, if the amount of each added is less than 0.1 part of merubian acid, the effect of the combined use is small. If it exceeds 0.4 parts by weight, the effect commensurate with the added amount will not be achieved and it is not practical.

In addition, by using two or more types of higher fatty acids and one or more metal salts of higher fatty acids in combination, molded products can be released easily during injection blow molding, have less uneven thickness, and can suppress the occurrence of sunspots. It will be done. Further, the amount of the metal salt of higher fatty acid added at that time is 0.05 to 0.15 parts by weight, and 0.0 to 100 parts by weight of the polystyrene resin or resin mixture.
If the amount is less than 5 parts by weight, there will be no effect, and if the amount is more than 0.15 parts by weight, the effect will not be commensurate with the amount added, which is not practical.

The higher fatty acid used in the present invention refers to a monocarboxylic acid having 10 or more carbon atoms and 1 or less unsaturation in the main chain, but from the viewpoint of compatibility with the resin, the number of carbon atoms is in the range of 10 to 24. is preferred.

For example, stearic acid (18 carbon atoms), behenic acid (22 carbon atoms), oleic acid (18 carbon atoms, 1 unsaturation),
Examples include erucic acid (22 carbon atoms, 1 unsaturation).

Further, the metal salts of higher fatty acids used in the present invention are metal salts of the above-mentioned higher fatty acids, and are not specified by the type of metal, but aluminum, calcium, magnesium, zinc, etc. are usually used. Higher fatty acids and metal salts of higher fatty acids may be added during polymerization of rubber-modified polystyrene resin and/or transparent polystyrene resin that is not modified with rubber, or may be added during the preparation of medium impact polystyrene, and in the present invention, they may be added. There are no restrictions on the timing or method of adding the additives.Furthermore, additives such as colorants, antistatic agents, and inorganic fillers that are commonly added to styrenic resins can also be added.

(Examples) The present invention will be described in detail below using Examples, but the present invention is not limited by the Examples.

First, in Experiments 1161 to 10, the effects of additives such as higher fatty acids and higher fatty acid metal salts on the phenomenon of poor molding were investigated.

After adding various additives to rubber-modified polystyrene having a volume average rubber particle diameter (dv) of 2.0 μm and a rubber concentration (Cr) of 3.0% by weight (dvXcr=6.0) and mixing with a blender. By kneading with an extruder, rubber-modified polystyrene and various additives were mixed and homogenized into pellets.

Injection blow molding was performed using these pellets, and defects in molding such as uneven thickness, poor mold release, and black spots were investigated. Table 1 shows additive formulations, and Table 3 shows data on molding defects for each formulation. Note that Experiments 41 to 6 are examples, and Experiments 167 to 10 are comparative examples.

Next, in Experiments/1611-18, the average rubber particle diameter (dv) and rubber concentration (Cr) of rubber-modified polystyrene were investigated.
We investigated the physical properties of a resin composition obtained by mixing and homogenizing rubber-modified polystyrene and additives when various changes were made (Table 2).

That is, 0.2 parts by weight of behenic acid, 0.2 parts by weight of stearic acid, and 0.1 parts by weight of zinc stearate were mixed with 100 parts by weight of rubber-modified polystyrene resin using a gorender, and the mixture was kneaded using an extruder to prepare pellets. A three-tiered grate and a lactic acid bacteria beverage container were molded using each of the samples thus created, and the opacity, compressive strength, and mouth strength were evaluated. Note that Experiments 411 to 14 are Examples, and Experiment 1
1615-18 are comparative examples.

In Experiment 11619, the physical properties of a resin composition obtained by mixing and homogenizing transparent polystyrene that is not modified with rubber, rubber-modified polystyrene, and additives were evaluated. in this case,
50 parts by weight of the rubber-modified polystyrene used in Experiment/1614 and the formulation and evaluation method modified with rubber are Experiment/1611~
It is the same as 18.

Table 2 shows the volume average rubber particle diameter (dv), rubber concentration (Cr), and product of both (dvXCr) of the rubber modified polystyrene resins used in Experiments A11 to A19.

Table 2 Volume average rubber particle diameter (dvλ) Value of rubber concentration (Cr) The additive formulation for Experiments 11611 to 19 was 100 parts by weight of (rubber-modified) polystyrene, 0.2 parts by weight of behenic acid, and 0.2 parts by weight of stearic acid. , zinc stearate 0.11i
-7 parts added.

Table 3: Thickness unevenness, mold release, black spots Table 4: Opacity, compressive strength, mouth strength Below, specific evaluation methods for thickness unevenness, mold release, black spots, opacity, waist strength, etc. in the above test will be explained.

Evaluation method Each sample was molded using an injection blow molding machine manufactured by Sumitomo Heavy Industries, Ltd.; Nebiomat 260/700508 with an internal capacity of 65
ml lactic acid bacteria beverage containers (12 pieces) were molded (cylinder temperature 230°C, injection pressure 1401ci/crt).
? , injection time 0.8 seconds, core temperature 110℃, blowing air pressure 6/crt? ) Evaluation was performed using the following method.

Uneven thickness: For each sample, one molding surface of the inverted mold after continuously molding 100 shots, here the upper rotating surface (12 shots)
A total of 60 pieces were collected for 5 consecutive shots. Since this molded product has a cylindrical part around its periphery, place it on a horizontal iron plate with a polishing degree (6.38 or less)') and a length of 300mm, and gradually lift one end of the molded product. Find the height at which it begins to roll. A molded product with a small thickness deviation will start rolling when lifted slightly, whereas a molded product with a large thickness deviation has a misaligned center of gravity, so the molded product will not roll unless one end of the iron plate is lifted high.

, - In this way, the rolling height of each molded product was determined.

Mold releasability: The releasability of a molded product from a hollow mold is determined by examining the percentage of molded products that do not fall normally and pop out when each molded product is ejected by pressurized air and released from the mold. It was evaluated.

Black spots: After molding the sample for thickness unevenness Y measurement, turn off the power to the molding machine with resin remaining in the tool and cylinder, leave it for 18 hours, and then turn the power to the molding machine again. The temperature was raised for 2 hours with the switch turned on. After confirming that the temperature of the cylinder, hot runner, etc. was sufficiently constant, 5 shots were blanked, and 10 shots were immediately molded.Among the 120 molded products obtained, the number of molded products with black spots was counted. , showed its incidence.

Opacity: The opacity of each sample was evaluated by making a flat plate with a thickness of 1 rrrIn by injection molding and examining its total light transmittance. Molding temperature is 220℃ Mold temperature is 40℃
It was ℃. The results are shown in Table 4.

Waist strength: The strength of the aforementioned lactic acid bacteria beverage container was measured. The strength was examined in two ways. The first is the compressive strength. The compression jig of the compression tester is a flat plate, the container is perpendicularly pressed against the flat plate, the container is compressed, and the load at which the container breaks is taken as the compressive strength.

The other factor is strength at the mouth. Use a compression jig as a weight on a compression tester, set the weight perpendicular to the weld line of the container, and perform compression to measure the load at the mouth when the container breaks. It was defined as strength. These results are summarized in Table 4.

(Effects of the Invention) As is clear from the above results, the resin composition of the present invention has good mold releasability, has few molding defects such as black spots, uneven thickness, etc.
Excellent opacity and molded product strength.

By using these resin compositions, injection blow molded products can be prevented from getting caught in the mold, uneven thickness, and black spots, and can also increase the opacity of hollow molded products to give them a high-class feel and improve the stiffness of hollow molded products. It is clear that the strength can be improved and its practical value is high.

Claims (1)

[Claims] Rubber concentration (Cr
) is 2.0 to 4.5% by weight, the volume average particle diameter (dv) of the rubber is 1.0 to 4.5 μm, and the value of dv × Cr is within the range of 4 to 18, and, based on 100 parts by weight of the resin or resin mixture, 0.1 to 0.4 parts by weight of two or more higher fatty acids each having a different number of carbon atoms of 4 or more, and a total amount of 0.3 to 0.8 parts by weight; A styrenic resin composition comprising 0.05 to 0.15 parts by weight of one or more higher fatty acid metal salts.