JPH0613619B2 - Foam molding method using a foaming agent that generates ammonia - Google Patents

Description

TECHNICAL FIELD The present invention relates to a foaming injection molding method using a foaming agent that generates ammonia, and an object thereof is to solve the problems caused by ammonia. .

(Prior Art) Foam molding is extremely useful because it is used for large-sized products such as cabinets of office equipment because of its moldability and ease of designing molded products.

In order to perform foam molding, it is generally adopted that a chemical foaming agent known per se is added to a resin at the time of molding and injection molding is carried out. Various compounds are known as chemical foaming agents.

Of these, the commonly used ones, such as azodicarbonamide, generate ammonia when decomposed, which gives the molded article an unpleasant odor, and ammonia also corrodes the metal incorporated in the molded article. There is a problem of doing.

In addition, it was necessary to remove the foaming agent residue called plate-out, which caused the deposition of the foaming agent residue on the surface. Therefore, a special process such as heat aging is required to remove ammonia. On the other hand, as a foaming agent which does not generate ammonia, for example, sodium hydrogen carbonate, barium carboxylate, 5-phenyltetrazole, or freon gas has been studied, but it is practically used in terms of handleability, safety, moldability and the like. Has not arrived yet.

(Problems to be Solved by the Invention) An object of the present invention is to suppress the generation of ammonia odor from a molded article when foaming injection molding is performed using a foaming agent that generates ammonia. As an additional purpose,
An object is to prevent plate-out of foaming agent residue on the surface of a molded product.

(Means for Solving Problems) The present invention provides a method of foaming and injection molding using a resin composition containing a thermoplastic resin and a blowing agent that generates ammonia, wherein the resin composition is a carboxyl group or a carboxylic anhydride. Provided is a method comprising containing a polymer having a group in an amount sufficient for suppressing an ammonia odor.

In the present invention, examples of the blowing agent that generates ammonia include azodicarbonamide, ammonium bicarbonate,
Dinitrozopentamethylenetetramine, nitrourea,
Examples thereof include hydrazodicarbonamide, nitroguanidine, triirazinotriazine, oxalyl hydrazide, p-toluenesulfonyl semicarbazide, p-methylurethanebenzenesulfonyl hydrazide, and 2,4-triiendisulfonyl hydrazide.

Examples of the polymer having a carboxyl group or a carboxylic acid anhydride group include C _{10 to} C ₃₀ aliphatic or aromatic monocarboxylic acids, dicarboxylic acids or dicarboxylic acid anhydrides. Further, α, β-dicarboxylic acid, α, β-dicarboxylic acid anhydride, α, ω-dicarboxylic acid and derivatives thereof such as maleic acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, adipic acid , Azelaic acid, sebacic acid, fumaric acid, succinic acid, maleic anhydride, citraconic anhydride, phthalic anhydride, maleenyl chloride, nadic acid anhydride, pyromellitic anhydride, succinic anhydride, trimellitic anhydride Can be used. As a polymer containing these as a functional group,
Examples thereof include those copolymerized with various polymers, for example, copolymers of styrene resins, petroleum resins, and olefin resins. Maleic anhydride, polystyrene modified with maleic anhydride, and petroleum resin modified with maleic anhydride are particularly preferable.
Also, a carboxylic acid derivative that gives a carboxyl group, such as an ester, can be used.

The amount of these polymers to be blended may be sufficient to suppress the ammonia generated from the foaming agent. Considering the reaction with ammonia, for example, in the case of azodicarbonamide, 2 equivalents of carboxyl are used per 1 mol of azodicarbonamide. The group is sufficient.

In the present invention, the polymer having a carboxyl group or a carboxylic acid anhydride group is contained in the resin composition by a means known per se, for example, a melt kneading means.

Examples 1 to 3 Polypropylene resin (Showa Denko KK, Shio Aroma MK110) was mixed with a maleic anhydride-grafted ethylene-ethyl acrylate copolymer having a maleic anhydride content of 6% at the following ratio, and 0.5 wt. % Azodicarboxylic acid amide was added, and foam injection molding was performed to examine the presence of ammonia odor and plate-out of the molded product.

The smell of ammonia was evaluated by a sensory test. The presence or absence of plate-out was determined by visual observation. In each case, evaluation was made from very good to extremely bad in five grades of ⊚, ○, Δ, ×, and XX.

Examples 4 to 6 A resin system composed of polyphenylene ether resin (PPO) and high impact polystyrene (HIPS) was mixed with maleic anhydride modified polystyrene having a maleic anhydride content of 6.2% by weight at the following ratio, 0.5% by weight of azodicarbonamide was added thereto, foaming injection molding was performed, and the presence or absence of ammonia odor and plate-out was examined.

Claims (1)

[Claims] 1. A method of foaming and injection molding using a resin composition containing a thermoplastic resin and a foaming agent that generates ammonia, wherein the resin composition has a carboxyl group or a carboxylic acid anhydride group for suppressing ammonia odor. A method characterized by containing a sufficient amount of