JPH0680858A - Polyoxymethylene resin composition - Google Patents

Abstract

PURPOSE:To obtain a new polyoxymethylene resin composition capable of improving the elongation and impact resistance without deteriorating excellent mechanical characteristics, etc., essentially possessed by the polyoxymethylene resin. CONSTITUTION:The objective new polyoxymethylene resin composition is essentially constructed from 50-99 pts.wt. polyoxymethylene polymer having the main chain in which a principal part is composed of a recurring unit of oxymethylene group (CH2-0) and 50-1 pt.wt. polyvinylphenolic resin or its derivative.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyoxymethylene polymer whose main chain main part is substantially composed of repeating units of an oxymethylene group-(CH ₂ -0)-and a polyvinylphenol resin or a derivative thereof. And a polyoxymethylene composition composed of

[0002]

2. Description of the Related Art Polyoxymethylene resins are excellent in mechanical strength, rigidity, creep resistance and solvent resistance, and are widely used mainly for mechanical parts such as automobiles, electric products and machines. Such excellent properties are largely due to the fact that polyoxymethylene is a highly crystalline resin, but on the other hand, its elongation and impact resistance are not at a sufficient level, and therefore such performance is required. It was difficult to apply it to various uses.

Although a mixed system has been reported for the purpose of solving these problems, a number of reports have been made since almost no resin compatible with polyoxymethylene is known due to its high crystallinity. Most of them were related to blends with thermoplastic elastomers such as polyurethane, and these were related to incompatible systems.

Recently, it has been reported that a novolak type phenolic resin is compatible with polyoxymethylene [Polymer Proceedings Vol. 47, 48 P.I. 443 (199
1)]. However, novolac type phenolic resins generally have a softening point of 80-
It was as low as 150 ° C., and there was a problem in processing such that the operability was difficult when kneading with polyoxymethylene in an extruder or the like.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a novel polyoxymethylene resin composition capable of improving elongation and impact resistance without significantly impairing the inherent properties of polyoxymethylene resin. To do.

[0006]

The present inventors have discovered that polyvinylphenol resins and their derivatives are extremely compatible with polyoxymethylene. Further, when the elongation of a mixture obtained by melt-kneading these resins with polyoxymethylene was measured, it was found that the value was significantly improved, and the present invention was completed.

That is, in the present invention, 50 to 99 parts by weight of a polyoxymethylene polymer in which the main part of the main chain is substantially composed of repeating units of oxymethylene group-(CH ₂ --O)-and polyvinylphenol resin or Derivatives 50-1
And a polyoxymethylene resin composition containing 1 part by weight. The present invention will be described in detail below.

Polyvinylphenol resins and their derivatives are extremely compatible with polyoxymethylene, and these resins are relatively easy to have a high molecular weight and easily have a high softening point (150 to 200 ° C.). Since it can be obtained, it has excellent kneadability. In addition, when the mechanical properties of the mixture obtained by kneading were measured, the mechanical elongation of the polyoxymethylene resin was not significantly impaired, and the mechanical elongation was greatly improved. It turned out to have.

In the present invention, polyvinylphenol is usually a polymer of p-vinylphenol having a vinyl group at the para position, and is a high molecular weight compound represented by the general formula of the following chemical formula 1 and usually having a number average molecular weight of 1,000 to 5,000. is there.

[0010]

[Chemical 1]

Generally, R = H is generally used, but an alkyl group substitution type such as methylation or t-butylation, or a substitution of a plurality of these substitution groups may be used. Further, derivatives thereof copolymerized with various monomers are also applicable to the present invention. For example, a styrene copolymer or a methyl methacrylate copolymer represented by the following chemical formula 2 can be applied.

[0012]

[Chemical 2]

Further, derivatives such as 2-hydroxyethyl acrylate copolymer, 2-hydroxyethyl methacrylate copolymer, butyl acrylate copolymer and the like can be applied. In each of the above copolymers, the composition ratio of vinylphenol and each of the copolymerization monomers is 10/90 or more, preferably 30/70 in terms of the molar ratio of vinylphenol / copolymerization monomer, from the viewpoint of compatibility with polyoxymethylene. As described above, more preferably 50/50 or more, that is, a higher proportion of vinylphenol is suitable. That is, it is considered that the contribution of the polyvinylphenol component is great in that the compatibility with polyoxymethylene is sufficiently exhibited even in these copolymers.

However, polyvinylphenol is a polymer having a phenol group, and this phenol group may impair the thermal stability of polyoxymethylene depending on its content. In this case, by using these copolymers, the compatibility, that is, the effect of improving the characteristics such as elongation drawn by the copolymer, and the thermal stability which is made possible by changing the composition ratio of vinylphenol and the copolymerization monomer. It is more preferable to use these copolymers in the present invention, because both of the controls can be easily dealt with according to the application in which the composition is used. Taking the above into consideration, the upper limit of the composition ratio of vinylphenol / copolymerized monomer is 95/5,
It is preferably 80/20.

The polyoxymethylene of the present invention is a polyoxymethylene polymer in which the main part of the main chain is substantially composed of repeating units of oxymethylene groups. For example, a polyoxymethylene homopolymer obtained by polymerizing formaldehyde or a cyclic oligomer of formaldehyde, such as trioxane and tetraoxane, the main chain of which consists mostly of oxymethylene chains, but of ethylene oxide or 1,3-dioxolane There is a polyoxymethylene copolymer obtained by adding 0.1 to 15 mol% of a cyclic ether having at least two adjacent carbon atoms to trioxane and polymerizing.

The copolymer is obtained, for example, by copolymerizing at least one polyfunctionally reactive compound copolymerizable with trioxane and at least one monofunctionally reactive compound copolymerizable with trioxane. Copolymers such as trioxane, 1,4-butanediol diglycidyl ether or bis (1,2,5-
Examples thereof include a copolymer obtained by copolymerizing pentanetriol) -triformal and ethylene oxide. This copolymer forms a polymer whose molecular chain is not linear but branched or networked. The present invention is also applicable to the above homopolymers and copolymers, and also to a mixture obtained by mixing the homopolymer and the copolymer in an appropriate ratio.

Further, the main part of the main chain is substantially composed of an acetalized product of polyoxymethylene, a reaction product with isocyanate, or a copolymer obtained by copolymerizing a small amount of a third component (for example, an alkyl group such as stearyl group). The present invention can be applied to any polyoxymethylene polymer that is composed of repeating units of oxymethylene groups. The present invention is a composition comprising 50 to 99 parts by weight of polyoxymethylene and 50 to 1 parts by weight of the above-mentioned polyvinylphenol or its derivative. In order not to impair the excellent properties inherently possessed by polyoxymethylene as much as possible, and in order to exhibit a more excellent effect by adding and mixing these, the composition ratio of polyvinylphenol and its derivatives suitable in the present invention is 30. Parts by weight or less, more preferably 2
It is 0 parts by weight or less. On the other hand, the lower limit is 1 part by weight or more, preferably 3 parts by weight or more, more preferably 5 parts by weight or more. Further, within the scope of the present invention, of course, the present invention also includes a mixture obtained by adding and mixing a mixture obtained by mixing the above-mentioned polyvinylphenol and its derivative with polyoxymethylene.

The composition of the present invention limits the composition ratio of polyoxymethylene and polyvinylphenol or a derivative thereof. In addition to these components, a third component, an additive and the like may be added if necessary. It can be added and mixed. For example, various additives such as hindered phenol-based antioxidants or polyamide-based heat stabilizers are usually used for polyoxymethylene for the purpose of improving the thermal stability. In the present invention, these various additives are used. May be included.

In the composition of the present invention, the degree of expression of the effect depends on the processing conditions. It is well known that normally crystalline resins have different mechanical properties depending on the cooling rate and solidification temperature during solidification after melting. It is considered that this is because the crystal growth condition changes due to the difference in the solidification conditions, resulting in a difference in the higher-order structure. The same tendency is observed in the composition of the present invention. For example, the lower the cooling temperature after melting or the faster the cooling rate, the more strongly the effect of the present invention is exhibited.
The crystallization temperature of polyoxymethylene is usually around 150 ° C., and the cooling temperature is lower than this, preferably 130 ° C.
It is below ℃.

The method for producing the composition of the present invention is not particularly limited. A commonly known method can be applied. Extruders are generally used industrially, and single-screw extruders, 2
Any of a twin-screw extruder may be used, but a twin-screw extruder having a superior kneading effect is more preferable.

[0021]

The present invention will be described in more detail with reference to examples. The tensile test shown in the examples was performed by the following method. A test piece having a length of 100 mm and a width of 10 mm was set at a chuck distance of 60 mm, a stress-strain curve was obtained at a strain rate of 50% / min at a temperature of 23 ° C. and a humidity of 50%, and each value was calculated from this result.

The thermostability is measured by thermogravimetric analyzer [K.
Shimadzu TGA-50] in a nitrogen atmosphere at 25
The change with time in weight loss was measured at 0 ° C., and the residual weight fraction (% by weight) after 30 minutes was obtained and this value was used as a measure of thermal stability.

[0023]

Example 1 Polyoxymethylene homopolymer having a number average molecular weight of about 60,000 containing only a hindered phenolic antioxidant and polyvinylphenol resin [Maruzen Petrochemical Co., Ltd.]
Maruka Linker M-S2 grade] having the composition shown in Table 1 were mixed in a drum blender, and each mixture was melt-kneaded at 200 ° C. by a screw type twin-screw extruder to form pellets. The melted strand at this time was transparent and pale yellow. The molten state of the pellets obtained here was observed under an optical microscope at a temperature equal to or higher than the melting point, and it was confirmed that the pellets were a transparent homogeneous phase and compatible with each other.

Next, the pellets of each composition were melted by hot pressing at 190 ° C., and each composition was melted at room temperature (25
C.), 120.degree. C., 140.degree. C., and quickly moved to a press for cooling and solidification, crystallized at that temperature, and then allowed to cool to room temperature. The thickness of the obtained press-formed product is about 200 μm.
Met. With respect to each cooling condition of each composition obtained by the above operation, a tensile test of each press-formed product was performed to measure the breaking strength and breaking elongation, and the results are shown in Table 1.
In addition, FIG. 1 illustrates the relationship between the elongation at break and the composition ratio of polyvinylphenol for each cooling condition. These results show that the composition of the present invention greatly improves the elongation at break without significantly deteriorating the original properties of polyoxymethylene due to its mechanical strength.

[0025]

[Table 1]

[0026]

Example 2 Copolymer of vinylphenol / styrene with a polyoxymethylene copolymer having a number average molecular weight of about 55,000 containing only a hindered phenolic antioxidant [vinylphenol / styrene = 70/30, Maruzen Petrochemical Marukalinker CST70 grade manufactured by Co., Ltd.] in the same composition ratio as in Example 1, and melt-kneaded in the same twin-screw extruder. The melted strand at this time was also transparent and pale yellow. Similarly, when the molten state of the pellet was observed under an optical microscope at a temperature equal to or higher than the melting point, it was confirmed that the pellet was a transparent homogeneous phase and was compatible.

Next, the pellets of each composition were similarly hot pressed, crystallized by a cooling and solidifying press set at 120 ° C., and then allowed to cool to room temperature. The thickness of the obtained press-formed product was about 200 μm. Similarly to Example 1, a press-molded article of each composition was subjected to a tensile test. FIG. 2 illustrates the relationship between the elongation at break and the composition ratio of the polyvinylphenol / styrene copolymer. These results show that, like Example 1, the composition of the present invention was greatly improved in its elongation at break.

[0028]

Example 3 To 80 parts by weight of the polyoxymethylene copolymer used in Example 2, 20 parts by weight of the polyvinylphenol resin of Example 1 and 80 parts by weight of the polyoxymethylene copolymer 80 were used.
20 parts by weight of the vinylphenol / styrene copolymer of Example 2 is added to 80 parts by weight of the polyoxymethylene copolymer, and 50/50 of vinylphenol / styrene is added to 80 parts by weight of the polyoxymethylene copolymer.
Copolymer [Maruzen Linker, Maruzen Petrochemical Co., Ltd.]
20 parts by weight of CST50 grade] were melt-kneaded to obtain three types of pelletized compositions. The thermal stability of each composition is shown in Table 2. This result shows that the use of the copolymer is superior in thermal stability.

[0029]

[Table 2]

[0030]

INDUSTRIAL APPLICABILITY The polyoxymethylene composition of the present invention can improve its mechanical elongation and impact resistance without significantly impairing the excellent mechanical properties inherent in polyoxymethylene. Therefore, it can be used for applications where these properties are conventionally insufficient and its application is difficult, and it is extremely useful from an industrial viewpoint.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the elongation at break and the composition ratio of polyvinylphenol at 25 ° C., 120 ° C. and 140 ° C.

FIG. 2 is a graph showing the relationship between the elongation at break and the composition ratio of a polyvinylphenol / styrene copolymer.

[Explanation of symbols]

 1 cooling solidification temperature, 25 ° C 2 cooling solidification temperature, 120 ° C 3 cooling solidification temperature, 140 ° C

Claims (1)

[Claims] 1. 50 to 99 parts by weight of a polyoxymethylene polymer in which the main part of the main chain is substantially composed of repeating units of an oxymethylene group — (CH ₂ —O) — and a polyvinylphenol resin or its derivative 50. To 1 part by weight of a polyoxymethylene resin composition.