KR20050080641A - Thermostable polyacetal resin composites - Google Patents

Abstract

The present invention is made by adding 0.1 to 10 parts by weight of an isocyanate compound and alcohols with respect to 100 parts by weight of polyacetal resin, the formaldehyde content by the PV3925 measuring method is less than 10 ppm and the functional smell by the PV3900 measuring method is 3 The present invention relates to a polyacetal resin composition having excellent thermal stability, which is a grade or less, and according to the present invention, the thermal stability, in particular, the molding processability is remarkably increased, so that the amount of formaldehyde can be maintained at an extremely low level even in harsh conditions, It is possible to provide a polyacetal resin composition that can be applied to sanitary and medical supplies, including interior materials and various interior products and piping materials.

Description

Thermally stable polyacetal resin composition {Thermostable polyacetal resin composites}

The present invention relates to a polyacetal resin composition excellent in thermal stability. In general, polyacetal resin is excellent in mechanical properties, fatigue resistance, friction-abrasion resistance, chemical resistance, and moldability, so that automotive parts, electrical and electronic device parts, precision mechanical parts, construction materials, piping materials, life-cosmetic products, and medical parts It has been widely used in such fields.

However, in recent years, there is a tendency for the demand for the quality of resins to increase with the expansion and diversification of the use. The properties required for polyacetal resins are that the mechanical strength should not be reduced in the extrusion or molding process, no deposits will occur in the mold, and the mechanical properties will not be degraded under long-term heating conditions. It is mentioned that the defective product of the thing is not generated, the formaldehyde which generate | occur | produces in a molded article, etc. are mentioned. Among them, decomposition of the polymer during heating acts as an important factor. In particular, polyacetal resins are inherently easily decomposed in a heat oxidation atmosphere or an acidic or alkaline atmosphere due to their chemical structure, which is an inherent task of polyacetal resins, which are highly thermally stable and suppress the formation of formaldehyde in the molding process or the molded article. Can be mentioned.

Formaldehyde is chemically active, forms formic acid by oxidation, adversely affects heat resistance, may cause corrosion of metal parts in molded assemblies, or discoloration due to the attachment of organic compounds. It may pollute the environment in the environment of use of the final product.

In order to stabilize chemically active unstable ends, homopolymers are used to acetylate the ends of polymers and esterify them. In copolymers, polymers are copolymerized with monomers having adjacent carbon bonds such as trioxane, cyclic esters, and cyclic formales. The method of decomposing and stabilizing an unstable terminal is known. However, when heated, decomposition occurs in the main chain portion of the polymer, and it is essential to add antioxidants and other stabilizers to prevent this.

Antioxidants, such as phenolic compounds with steric hindrance, amine compounds or other stabilizers, such as melamine derivatives, polyamides, and polyacrylamides, as a means of inhibiting formaldehyde generation of polyacetal resins Nitrogen-containing compounds, alkali metal hydroxides, alkaline earth metal hydroxides, organic acids or inorganic acid salts and the like are already known. Melamine derivatives of these stabilizers are relatively effective and typically antioxidants are used in combination with other stabilizers.

However, even when blended with these additives, it is difficult to completely inhibit the decomposition of the polyacetal resin, to impart high thermal stability and to greatly reduce the generation of formaldehyde. Therefore, in reality, formaldehyde is generated at the end of decomposition of the main chain or the end that is not sufficiently stabilized by the action of heat or oxygen in the cylinder of the extruder or the molding machine during the extrusion or the melt processing in the molding plant to prepare the composition. Deteriorates the working environment during machining. In addition, when the mold is formed for a long time, the fine powder and the tar material are attached to the mold, and the work efficiency is reduced, and the surface state of the molded product is poor. In addition, deterioration of physical properties due to decomposition of the polymer and discoloration of the resin occur. In addition, in order to suppress the generation | occurrence | production of formaldehyde in the processing process of a polyacetal resin composition and a molded article, the said method is not suitable.

Japanese Patent Application Publication No. 80-50502 and Japanese Patent Application Publication No. 94-73267 propose to improve mold adhesion by improving thermal stability by using a high molecular weight melamine derivative by polycondensation of melamine and formaldehyde. Even when using a molecular weight melamine derivative, it was difficult to significantly reduce the amount of formaldehyde produced.

In addition, Japanese Patent Application Laid-Open No. 73-88135 proposes stabilization including nitrogen-containing compounds such as phenolic compounds, hydantoins and derivatives thereof in order to improve the thermal stability and the antioxidant properties of polyacetals. It was difficult to keep at a low level.

Accordingly, the present invention provides a resin composition which improves the thermal stability of polyacetal resin, in particular the melt stability during molding, by reducing the amount of formaldehyde in the final product so as to solve all the problems of the prior art as described above. Let it be technical problem.

In order to solve the above problems, the present inventors have examined the relationship between the thermal stability of a conventional polyacetal resin and a series of urethane derivatives. As a result, an isocyanate compound having a specific chemical structure has a thermal stability, in particular, melt processing of a polyacetal resin. It has been found to have a remarkable effect as a stabilizer, and that the combination of the isocyanate compound and the alcohol compound can significantly increase the thermal stability, especially the molding processability, so that the formation of formaldehyde can be maintained at an extremely low level even under severe conditions. The invention was completed.

Therefore, according to the present invention, in the polyacetal resin composition,

0.1 to 10 parts by weight of isocyanate compound and alcohols are added to 100 parts by weight of polyacetal resin, formaldehyde content is less than 10 ppm by PV3925 measuring method, and odor grade is less than grade 3 by PV3900 measuring method. Provided is a polyacetal resin composition having excellent thermal stability.

Hereinafter, the present invention will be described in more detail.

The polyacetal resin composition of the present invention consists of a polyacetal resin, an isocyanate compound and alcohols. The polyacetal resin may be a homopolymer or copolymer of polyoxymethylene having a melting point of 160 ° C. or higher, a crystallinity of 65 to 80%, and a number average molecular weight of 10,000 to 200,000. It is preferable to use 90 to 99.9 parts by weight of such homopolymer or copolymer with respect to the total resin composition.

The isocyanate compound may be any one selected from the group consisting of aromatic isocyanates, aliphatic isocyanates, cyclic isocyanates, derivatives and mixtures thereof. As said aromatic isocyanate, 1, 4- phenylenedi isocyanate, 2, 4- toluene diisocyanate, 2, 6-toluene diisocyanate and mixtures thereof, 2, 2- methylene diphenyl diisocyanate, 2, 4- methylene diphenyl Diisocyanate, 4,4-methylenediphenyl diisocyanate, naphthalene diisocyanate and the like. Moreover, cycloaliphatic diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, etc. are contained as said aliphatic isocyanate or cyclic aliphatic isocyanate.

Alcohols used in the present invention include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 2-methylpentanediol, 1,3-pentanediol, 1 , 6-hexanediol, 1,4-cyclohexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, neopentylglycol and the like can be used alone or in combination.

In the present invention, the isocyanate compound and alcohols are preferably mixed at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the total resin composition. If the content is less than 0.1, the effect of reaction with formaldehyde is insufficient, and the formaldehyde content is high. There is a lot of smell, the addition effect is insufficient, and if it exceeds 10, it may lead to the deterioration of mechanical properties. More preferably, 0.2 to 5.0 weight part is good. In addition, at least one additive selected from the group consisting of a release agent, an antioxidant, a filler, a colorant, a reinforcing agent, a tube stabilizer, and a pigment may be further added to the resin composition of the present invention. The additives can be used in a range that does not substantially affect the physical properties of the composition of the present invention. Alkylene bis steamides, waxes and polyether glycid may be used as the release agent. Preferably, ethylene bis steamides are used. Preferred as antioxidants are hindered bisphenols, particularly triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate.

In the present invention, it is possible to provide a polyacetal resin composition having improved moldability by mixing together a polyacetal resin, an isocyanate compound and alcohols. Moreover, in this invention, the molded article which consists of said polyacetal resin composition is also included.

The isocyanate and alcohol may react with the alcohol group of the polyacetal resin and the isocyanate in-situ during melt kneading to generate a block copolymer of polyoxymethylene / polyurethane, and the additive remaining in the unreacted state is heated during molding. It is necessary to pay attention to its content so that additives to be added do not remain unreacted because it may cause gas generation and change over time due to poor stability and surface defects of molded products. Therefore, in order to obtain a composition suitable for the purpose of the present invention, the equivalent ratio of isocyanate to alcohol is preferably 0.99 to 1.10, more preferably 1.01 to 1.05. If the equivalent ratio is less than 0.99, the isocyanate may not sufficiently stabilize the unstable hydroxy end of the polyacetal resin, so that the unstable hydroxy end of the polyacetal resin remaining during processing may be decomposed, resulting in formaldehyde. Formaldehyde gas can be generated during molding and flow out into the atmosphere to feel the smell, and formaldehyde remains in the molded article, causing odor in the molded article.

On the other hand, if the equivalent ratio exceeds 1.10, the unstable end can be stabilized, and there is a desirable effect of not being able to feel the smell by reacting with formaldehyde gas generated during molding, but it is possible to reduce the mechanical properties, particularly the tensile strength and impact strength. It is not desirable to cause.

The polyacetal resin composition of the present invention can suppress the formation of by-products of the mold while maintaining mechanical properties, and the formaldehyde content (by PV3925 measurement method) in the molded product is 10 ppm or less, more preferably 7 ppm or less, and toxic in smell. It can provide polyacetal resin of grade 3 or less (by PV3900 measuring method) which is not able to feel the level and can be applied to sanitary and medical products including automobile interior, various interior and piping materials.

 In the following examples, non-limiting examples of preparing the polyacetal resin of the present invention are given.

[Examples 1-4 and Comparative Examples 1-4]

After drying polyoxymethylene resin (trade name: coacetal K300 (MI 9/10 min), manufacturer: KTP) at 80 ° C. for 4 hours in a vacuum, the antioxidant, isocyanate and alcohol were mixed according to the composition ratio of Table 1 below. Feed through primary or twin-screw extruder. Melt kneading is carried out at a temperature of 190 ℃ using a compressor. This is discharged into a spaghetti type through a die, cooled and cut into pellets using a pelletizer. After drying the resin composition thus obtained, the specimen for measuring the dumbbell-type property at 190 ° C was injection molded and evaluated for mechanical properties.

The properties evaluated in the present invention are tensile strength and elongation ASTM D-638 method, impact strength ASTM D-256 method, formaldehyde content PV-3925, odor is shown in Table 2 after evaluation by PV-3900 It was.

division Polyoxymethylene resin (part by weight) Isocyanate (parts by weight) Alcohol (part by weight) Example 1 100 Hexamethylene diisocyanate, 0.146 Ethylene glycol, 0.054 Example 2 100 Phenylenediisocyanate, 0.456 1,4-butanediol, 0.244 Example 3 100 Phenylenediisocyanate, 0.037 Ethylene glycol, 0.013 Example 4 100 Hexamethylene diisocyanate, 3.267 1,4-butanediol, 1.733 Comparative Example 1 100 0 0 Comparative Example 2 100 Hexamethylene diisocyanate, 0.141 Ethylene glycol, 0.259 Comparative Example 3 100 Hexamethylene diisocyanate, 1.126 1,4-butanediol, 0.344 Comparative Example 4 100 Phenylenediisocyanate, 7.706 1,4-butanediol, 4.294

division Tensile strength (㎏ / ㎠) % Elongation Impact strength (kgcm / cm) Formaldehyde content (ppm) Odor (Grade) Example 1 603 51 5.9 6.1 3 Example 2 587 63 6.1 4.3 2 Example 3 611 58 6.0 7.1 3 Example 4 597 74 7.4 2.6 2 Comparative Example 1 624 48 5.7 27.5 4 Comparative Example 2 512 28 4.0 14.2 4 Comparative Example 3 524 31 3.7 3.8 2 Comparative Example 4 461 79 13.5 6.7 2

As a result of the evaluation of the characteristics it can be seen that the formaldehyde content of the molded specimen is 7ppm or less while maintaining the mechanical properties, the odor evaluation of the sensory test has an effect of showing the results of less than three grades without stimulation.

As described above, the present invention can suppress the generation of by-products in the mold due to high thermal stability during molding while maintaining the mechanical properties of the polyacetal resin, and the formaldehyde content in the molded article is 10 ppm or less, more preferably 7 ppm Below, it can provide a polyacetal resin of grade 3 or less that can not feel the toxicity even in the smell, useful inventions that can be applied to sanitary and medical products, including interior materials and various interior and piping materials of automobiles to be.

Claims (4)

In the polyacetal resin composition, 0.1 to 10 parts by weight of isocyanate compound and alcohols are added to 100 parts by weight of polyacetal resin, formaldehyde content is less than 10 ppm by PV3925 measuring method, and odor grade is less than grade 3 by PV3900 measuring method. A polyacetal resin composition excellent in thermal stability. The polyacetal resin composition having excellent thermal stability according to claim 1, wherein the equivalent ratio of isocyanate to alcohol is 0.99 to 1.10. The polyacetal resin composition having excellent thermal stability according to claim 1, wherein the isocyanate compound is any one selected from the group consisting of aromatic isocyanates, aliphatic isocyanates, cyclic isocyanates, derivatives and mixtures thereof. The method of claim 1, wherein the alcohols are ethylene glycol, diethyltenglycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 2-methylpentanediol, 1,3-pentanediol, It is any one selected from the group consisting of 1,6-hexanediol, 1,4-cyclohexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, neopentin glycol and mixtures thereof. A polyacetal resin composition excellent in thermal stability.