JPS642059B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a double injection molded product with improved environmental stress cracking resistance, which is made of a composite ABS containing EVA and a vinyl chloride resin containing a plasticizer. For ABS, the surface of the molded product is coated with other materials for design purposes or to improve weather resistance, and the other materials used here are generally metals or paints. It is. Sometimes, there is a demand to coat part or all of ABS molded products with vinyl chloride resin containing plasticizers, mainly for design purposes, but when ABS and vinyl chloride resin come into contact, the contact surface Cracks occur on the ABS side, and in severe cases, accidents often occur where it breaks. This phenomenon occurs when the plasticizer contained in the vinyl chloride resin migrates to the ABS side, causing ABS to undergo environmental stress cracking fracture due to the plasticizer, and is caused by the poor environmental stress cracking resistance of ABS due to the plasticizer. It is something to do. Attempts have been made to improve the environmental stress cracking resistance of ABS to plasticizers, such as increasing the molecular weight of the resin phase, increasing the acrylonitrile content of the resin phase, and increasing the rubber component content. None of the methods resulted in a practically sufficient improvement effect. For this reason, ABS is not normally used in contact with a vinyl chloride resin containing a plasticizer, which limits the uses of ABS. In particular, when double injection molding of ABS and vinyl chloride resin is used to make an integral molded product, cracks occur in the ABS of both resins due to residual stress during the double injection molding, making it impossible to make a molded product that can withstand practical use. I can't. As a result of intensive study on a method for preventing environmental stress crack failure in double injection molding made of vinyl chloride resin containing ABS and plasticizer, the inventor found that 100 parts by weight of ABS and 0.1 to 5 parts by weight of EVA were added to 100 parts by weight of ABS. We discovered that in a double injection molded product made of a mixed composite ABS and a vinyl chloride resin containing 1% by weight or more of a plasticizer, no cracks occur in the ABS on the contact surface, and we have completed the present invention. I've reached it. The double injection molded product according to the present invention is suitable for use in automobile parts and the like because the phenomenon of cracking caused by plasticizer migration is eliminated. The ABS used in the present invention consists of a rubber phase and a resin phase, and diene rubber, acrylic rubber, EPDM rubber, etc. can be used as the rubber phase, and diene rubber is particularly preferred. Specific examples of the diene rubber phase include polybutadiene, polyisoprene, poly(butadiene-styrene), poly(butadiene-acrylonitrile), poly(butadiene-methyl methacrylate), and the resin phase includes poly(acrylonitrile-styrene). ,
Examples include poly(acrylonitrile-methyl methacrylate-styrene) and poly(acrylonitrile-α-methylstyrene-styrene). The diene rubber phase may be a mixture of two or more diene rubbers, and the resin phase may also be a mixture of two or more resins. Preferably, the ABS used in the present invention contains 5 to 30% by weight of rubber. If the rubber content is less than 5% by weight, the resin obtained by mixing with EVA will not have sufficient plasticizer resistance, and if it exceeds 30% by weight, the rigidity will decrease. There are no particular restrictions on the manufacturing method of ABS.
Known polymerization techniques are applied. The EVA used in the present invention is a copolymer containing ethylene and vinyl acetate, and in some cases, these two types of monomers and a vinyl monomer copolymerizable with them. The copolymerizable vinyl monomers used here include (meth)acrylic monomers such as ethyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, and methyl methacrylate, styrene, and α-methylstyrene. , styrene monomers such as vinyltoluene, lytrile monomers such as acrylonitrile and methacrylonitrile, and halogen-containing monomers such as vinyl chloride and vinylidene chloride. There are no particular restrictions on the EVA polymerization method, and known polymerization techniques can be applied. The EVA used in the present invention has a glass transition temperature of
It is desirable that the temperature is 20°C or lower, preferably 10°C or lower. When the glass transition temperature exceeds 20℃,
The resin obtained by mixing with ABS has low plasticizer resistance, which is not preferable. EVA used in the present invention has a solubility parameter of 8.4 to 10.0 (cal/cc) ^1/2 , preferably 8.7 to 9.7.
(cal/cc) Desirably in the range of ^1/2 . If the solubility parameter deviates from the above range,
The resin obtained by mixing with ABS has low plasticizer resistance, which is not preferable. The solubility parameter here uses the solubility parameter value described in "Polymer Handbook" published by John Wiley & Sons, and the solubility parameter δ _T of the copolymer is m
It is calculated by formula (1) from the solubility parameter δ _o of the homopolymer of each vinyl monomer constituting the copolymer composed of different types of vinyl monomers and its weight fraction W _o . Equation (1) δ _T = _n 〓 ⁿ⁼¹・δ _o W _o ／ _n 〓 ⁿ⁼¹ W _o [(cal/cc) ^1/2 ] For example, the solubility parameters of polyethylene, polyvinyl acetate, and polybutyl acrylate are respectively 8.1, 9.4, 8.8, ethylene 15% by weight, vinyl acetate 70% by weight, butyl acrylate 15% by weight
The solubility parameter δ _T of the copolymer consisting of is 9.1
It is calculated as follows. The EVA used in the present invention preferably has a gel content of 50% by weight or less. If the gel content of EVA exceeds 50% by weight, the resin obtained by mixing with ABS will have low plasticizer resistance, which is undesirable. Note that the gel content referred to herein is determined by the following method. That is, EVA is added to 100 g of methyl ethyl ketone and stirred vigorously at room temperature for 6 hours. This was centrifuged at 15000 rpm for 1 hour.
Determine the dry weight of the precipitate. To the resulting dry weight
Multiply by 100 to obtain gel content (wt%). In the present invention, EVA0.1 to 100 parts by weight of ABS
Add 50 parts by weight, preferably 1 to 30 parts by weight.
If the amount of EVA added is less than 0.1 part by weight, the plasticizer resistance of the resin obtained by mixing with ABS will not be sufficient, and if it exceeds 50 parts by weight, not only will the effect be saturated,
This is not preferable because the rigidity of the resin obtained by mixing with ABS decreases. In the present invention, a mixing process of ABS and EVA is required, but there are no particular restrictions on the mixing method. When EVA is manufactured by emulsion polymerization,
A method of mixing EVA latex and ABS latex and recovering the resin, a method of mixing EVA latex and ABS powder with a mixer and feeding it to an extruder, a method of adding EVA latex to ABS melt and melt-kneading it, etc. A mixture can be obtained by If EVA is available as a solid, the mixture can be obtained by mixing it with ABS in a mixer and feeding it into an extruder. The vinyl chloride resin used in the present invention is a homopolymer or copolymer having vinyl chloride as a constituent unit. Monomers constituting the vinyl chloride copolymer include halogenated vinyl monomers such as vinylidene chloride, ethylene, propylene, 1-butene,
Olefin monomers such as 2-butene, isobutylene, norbornene, diene monomers such as butadiene, isoprene, chloroprene, (meth) acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, methyl methacrylate, etc. Acrylic monomer, acrylonitrile,
Nitrile monomers such as methacrylonitrile, styrene monomers such as styrene, α-methylstyrene, and vinyltoluene, vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, and phenyl vinyl ether, and fatty acid vinyls such as vinyl acetate. There are monomers, etc., and these can be used alone or in combination. There are no particular restrictions on the method of polymerizing the vinyl chloride resin, and known techniques such as emulsion polymerization and suspension polymerization can be applied. In addition, the vinyl chloride resin used in the present invention can be mixed with other polymers for modification, but the other polymers used here include ABS, poly(methyl methacrylate-butadiene-styrene), poly(methyl methacrylate-butadiene-styrene), Methyl methacrylate, poly(methyl methacrylate-butyl acrylate), nitrile rubber,
These include epichlorohydrin rubber, EVA, poly(ethylene-propylene) rubber, and poly(styrene-butadiene) rubber. Furthermore, the vinyl chloride resin used in the present invention contains 1% by weight or more of a plasticizer, and examples of the plasticizer used here include dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dibutyl phthalate, diheptyl phthalate, and dioctyl phthalate. , phthalate esters such as dinonyl phthalate, diisodecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, diisodecyl succinate, dioctyl adipate, diisodecyl adipate, dioctyl azelate,
Aliphatic dibasic acid esters such as dibutyl sebacate, dioctyl sebacate, and dioctyl tetrahydrophthalate; glycol esters such as diethylene glycol dibenzoate and dipentaerythritol hexaester; fatty acid esters such as butyl oleate and methyl acetyl ricinoleate; Phosphate esters such as sulfophosphate, trioctylphosphate, triphenylphosphate, trichloroethylphosphate, epoxidized soybean oil, epoxidized linseed oil, butyl epoxy stearate, octyl epoxy stearate, etc. The compounds include trioctyl trimellitate, ethyl phthalyl ethyl glycolate, butylphthalyl butyl glycolate, and tributyl acetyl citrate. These plasticizers can be used alone or in combination. In the present invention, composite ABS containing EVA and vinyl chloride resin are double injection molded, but conventional techniques and equipment can be used as they are for the double injection molding method and apparatus. A double injection molded product refers to a molded product that is made up of parts made of two different materials. To obtain a double injection molded article, a double injection molding machine or two independent injection molding machines may be used. A dual injection molding machine has two injection mechanisms, each of which injects material separately.
Further, there are cases in which there are two mold clamping mechanisms, but there are also cases in which the molds have a mechanism in which two molds rotate within a single mold clamping mechanism. In either case, molded products injection molded from separate injection mechanisms are combined in a mold to form a single molded product. independent 2
When using two injection molding machines, the first injection molding machine injects the first material, then this molded product is assembled inside the mold of the second injection molding machine, and the second injection molding machine The machine injects the second material into a single molded article. The double injection molded product of the present invention has a vinyl chloride resin containing EVA as an essential constituent unit, but depending on the purpose, a multiple injection molded product can have other resins as a constituent unit. Other resins mentioned here include polystyrene, high impact polystyrene, poly(styrene-methyl methacrylate),
ABS, styrenic resins such as poly(acrylonitrile-acrylic acid ester-styrene) (AAS), poly(acrylonitrile-EPDM-styrene) (AES), olefin resins such as polyethylene, polypropylene, chlorinated polyethylene, chlorinated polypropylene, These include polymethyl methacrylate resin, polyamide resins such as nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, and nylon 12, polycarbonate resins, polysulfone resins, and polyphenylene oxide resins, but they cannot be combined with vinyl chloride resins. It is preferable to use styrene resins, polymethyl methacrylate resins, polycarbonate resins, etc., which cause environmental stress cracking upon contact, while avoiding contact with vinyl chloride resins. As explained above, the double injection molded product of the present invention has composite ABS containing EVA and vinyl chloride resin as constituent units, and the composite ABS containing EVA has excellent environmental stress cracking resistance against plasticizers. Because of its excellent properties, cracks do not occur in the composite ABS at the interface when double injection molded with vinyl chloride resin containing plasticizer. For this reason, the molded product of the present invention is made of ordinary ABS.
Accidents caused by cracks that frequently occur in double-injection molded products made of polyvinyl chloride resin and polyvinyl chloride resin are prevented, and the product is suitable for use in automobile parts, light electrical parts, miscellaneous goods, etc. It is a constituent unit of the double injection molded product of the present invention.
Composite ABS containing EVA is suitably used not only in double injection molded products but also in other embodiments in which it comes into contact with vinyl chloride resin containing a plasticizer. The present invention will be further explained below with reference to Examples, and all parts and percentages stated in the specification are expressed on a weight basis. Example 1 100 parts of ABS powder consisting of 15% butadiene, 23.8% acrylonitrile, and 61.2% styrene and 10 parts of EVA latex (in terms of solid content) of samples No. A to J shown in Table 1 were mixed in a Henschel mixer. rear,
Composite ABS pellets were obtained by feeding into an extruder. This composite ABS is manufactured by Toshiba Machine Co., Ltd. IS80CN―
Injection molded with a V injection molding machine at a molding temperature of 220℃,
A flat molded product measuring 200 x 30 x 3 mm was obtained. This molded product was fitted into a mold with cavity dimensions of 200 x 30 x 6 mm, and sample No. shown in Table 2 was obtained.
A vinyl chloride compound of K was injection molded using the injection molding machine described above at a molding temperature of 150°C to obtain a double injection molded product. The environmental stress cracking resistance of the obtained double injection molded product was evaluated by the following method. This double injection molded product was strained by 30 mm, fixed in a jig, and left in a constant temperature bath at 60°C for 5 days. After 5 days, the molded product was removed from the jig, the vinyl chloride layer was peeled off, and the surface condition of the composite ABS molded product was observed. The environmental stress cracking resistance of the composite ABS molded product was evaluated by the following method, and the results are summarized in Table 3. Almost no change; Fine cracks occur at both ends of the molded product; Fine cracks cross the molded product; Thick cracks cross the molded product; Cracks grow deep and break immediately when bent; Breaking Example 2 100 parts of the ABS powder used in Example 1 and 10 parts of EVA latex of sample No. A shown in Table 1 (solid content equivalent)
After mixing with a Henschel mixer, the mixture was fed to an extruder to obtain composite ABS pellets. This composite ABS was injection molded in the same manner as in Example 1 to obtain a flat molded product. This molded product was fitted into a mold with cavity dimensions of 200 x 30 x 6 mm, and sample No. shown in Table 2 was obtained.
The vinyl chloride compounds L to Q were injection molded in the same manner as in Example 1 to obtain double injection molded products. This double injection molded product was evaluated in the same manner as in Example 1, and the results are summarized in Table 4. Example 3 To 100 parts of the ABS powder used in Example 1, 1 to 30 parts (in terms of solid content) of EVA latex of Sample No. A shown in Table 1 was added to obtain composite ABS pellets. This composite ABS was injection molded in the same manner as in Example 1 to obtain a flat molded product. This molded product was fitted into a mold with cavity dimensions of 200 x 30 x 6 mm, and sample No. shown in Table 2 was obtained.
The vinyl chloride compound of K was injection molded in the same manner as in Example 1 to obtain a double injection molded product. This double injection molded product was evaluated in the same manner as in Example 1, and the results are summarized in Table 5. Example 4 80 parts of ABS latex (in terms of solid content) consisting of 40% butadiene, 17.4% acrylonitrile, and 42.6% styrene and 20 parts of EVA latex of sample No. A shown in Table 1 (in terms of solid content) were mixed in a latex state. Mixed as is. An aqueous calcium chloride solution was added to this mixed latex, and the mixture was heated and stirred to precipitate a latex. The resulting slurry is filtered, washed with water, dried and composited.
ABS powder was obtained. 100 parts of this composite ABS and 100 parts of AS resin (acrylonitrile 30%, styrene 70%) were mixed and fed to an extruder to obtain pellets. The obtained pellets were injection molded in the same manner as in Example 1 to obtain a plate-shaped molded product. This molded product was fitted into a mold with cavity dimensions of 200 x 30 x 6 mm, and sample No. shown in Table 2 was obtained.
The vinyl chloride compound of K was injection molded in the same manner as in Example 1 to obtain a double injection molded product. This double injection molded product was evaluated in the same manner as in Example 1, and as a result, the environmental stress cracking resistance was ranked as . Comparative Example 1 Various types of ABS shown in Table 6 were injection molded using the injection molding machine used in Example 1 to obtain flat molded products of 200 x 30 x 3 mm. The molding temperature of various ABS is determined by experiment.
Nos. 24, 25, and 26 were at 220℃, Experiment No. 27 was at 260℃, and Experiment No.
28 and 29 were conducted at 270°C. This molded product was fitted into a mold with cavity dimensions of 200 x 30 x 6 mm, and sample No. shown in Table 2 was obtained.
The vinyl chloride compound of K was injection molded in the same manner as in Example 1 to obtain a double injection molded product. This double injection molded product was evaluated in the same manner as in Example 1, and the results are summarized in Table 6. The melt flow index in the table is ASTM
Measured in accordance with D-1238, temperature 250℃,
The test was carried out with a load of 5 kg. In addition, the ABS of Experiment No. 24 was used in Example 1.
It is ABS. Comparative Example 2 55 parts of EVA latex of sample No. A shown in Table 1 was added to 100 parts of the ABS powder used in Example 1 (solid content equivalent).
was added to obtain composite ABS pellets. When this composite ABS was evaluated for environmental stress cracking resistance according to the method of Example 1, it was ranked as . However, this double injection molded product had extremely low rigidity and was evaluated to be impractical.

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Claims (1)

[Claims] 1. A double injection molded product consisting of a composite ABS in which 100 parts by weight of ABS is mixed with 0.1 to 50 parts by weight of EVA, and a vinyl chloride resin containing 1% by weight or more of a plasticizer.