JPH05239312A - Polyoxymethylene resin composition having low gloss - Google Patents

Abstract

PURPOSE:To obtain a polyoxymethylene resin composition excellent in low glass property without impairing characteristic mechanical physical properties of a polyoxymethylene resin by adding a multiphase interpolymer having a specific composition to the polyoxymehyene resin. CONSTITUTION:The objective polyoxymethylene resin composition having low gloss property is obtained by blending (A) 50-99wt.% resin consisting of a polyoxymethylene homopolymer, branched polymer and block copolymer with (B) 1-50wt.% multiphase interpolymer having preferably <=1mum particle diameter and composed of B1: a middle core phase consisting essentially of a polymer of an ester of (meth)acrylic acid and 1-12C alkyl alcohol (preferably ethylhexyl acrylate) and containing no graft polymer and B2: outer core phase consisting of a polymer of an ester (preferably butyl acrylate or methyl methacrylate) of (meth)acrylic acid and 1-4C alkyl alcohol, containing no graft polymer and having a composition different from that of the component B1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyoxymethylene resin composition having low gloss while maintaining the original properties of polyoxymethylene resin.

[0002]

2. Description of the Related Art Conventionally, polyoxymethylene resins have high mechanical strength, and are excellent in rigidity, creep resistance, solvent resistance, slidability and the like, and have light weight and good moldability. Widely used as a representative engineering resin in such fields. However, high gloss, which is one of the characteristics of polyoxymethylene resin, is regarded as a defect in some fields of use. In the case of automobile interior parts, the interior is given a high-class and profound feeling by reducing the gloss along with the seat cover and other resins. In addition, the low gloss has been devised so that the interior material is not reflected on the windshield and the driver is not dazzled. Further, in the field of optical equipment, low-gloss materials are regarded as important in order to prevent erroneous operation of equipment due to reflection of light.

Therefore, various methods for reducing the gloss have been studied. BACKGROUND ART A method is known in which a surface of a mold is subjected to a texturing process to make unevenness on the surface of a molded product and transferred to the surface of the molded product, and a method of applying a low-gloss coating. However, even if the polyoxymethylene resin is molded with a textured mold, the mold deposit (mold contamination) covers the textured surface, and a sufficiently low gloss surface cannot be obtained. Low-gloss coating is not an effective means because there is no paint that adheres strongly to the polyoxymethylene resin surface.

As a method of reducing the gloss of the polyoxymethylene resin itself, a method of blending an inorganic filler with the polyoxymethylene resin is known (Japanese Patent Laid-Open No. 64-5).
4053, JP-A-1-170641, JP-A-1-319561). The polyoxymethylene resin composition containing these inorganic fillers has minute irregularities on the surface of the molded product, and thus diffusely reflects the irradiated light and can reduce the glossiness, but the degree of the effect is Not enough. Furthermore, the polyoxymethylene resin composition containing the inorganic filler has a drawback that mechanical properties, particularly elongation and toughness, are extremely lowered, and the original characteristics of the polyoxymethylene resin are impaired.

On the other hand, as a method of adding a multiphase interpolymer to a polyoxymethylene resin, a method of adding an acrylic multiphase interpolymer having a two-phase structure to a polyoxymethylene resin (Japanese Patent Laid-Open No. 59-136343). , A method of adding a rubber elastic graft copolymer having a glass transition temperature of −20 ° C. or lower to an oxymethylene polymer (Japanese Patent Publication No. 48-34830), and a rubber elastic graft polymer having butadiene to a polyoxymethylene resin. A method of adding (JP-A-61-120849),
A method of blending a core-shell polymer having no graft bond with an engineering plastic (JP-A-2-12)
No. 9266) is known, but any of the compositions obtained by the above-mentioned method significantly impairs the mechanical properties (particularly strength and elastic modulus) inherent to the polyoxymethylene resin, and the thermal stability during molding is unsatisfactory. It has problems such as being sufficient. Moreover, none of the compositions obtained by the above method is intended for low glossiness, so the degree of low glossiness was not sufficient.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to overcome the drawbacks of the prior art, to maintain the original mechanical properties of polyoxymethylene resin, and to realize sufficient low gloss polyoxymethylene. It is to provide a resin composition.

[0007]

Means for Solving the Problems As a result of intensive studies made by the present inventors in order to solve the above problems, polyoxymethylene obtained by adding a multiphase interpolymer having a specific composition to a polyoxymethylene resin. The present inventors have found that the resin composition has extremely excellent low gloss and does not impair the mechanical properties inherent to the polyoxymethylene resin, thus leading to the present invention.

That is, the present invention comprises (A) a polyoxymethylene resin of 50 to 99% by weight, (B) a core phase and an outer shell phase, and (a) the core phase is acrylic acid or methacrylic acid and a carbon number. A polymer containing, as a main component, at least one monomer selected from the group consisting of esters with alkyl alcohols of 1 to 12, and not including a graft polymer,
(B) The outer shell phase is a polymer containing at least one monomer selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 4 carbon atoms as a main component and not containing a graft polymer. A low gloss polyoxymethylene resin composition comprising 1 to 50% by weight of a phase interpolymer is provided.

The present invention will be described in detail below. The (A) polyoxymethylene resin used in the present invention is substantially oxymethylene produced from a cyclic oligomer such as formaldehyde monomer or its trimer (trioxane) or tetramer (tetraoxane). Oxymethylene having 2 to 8 carbon atoms, which is produced from an oxymethylene homopolymer consisting of a unit and the above-mentioned raw material and a cyclic ether such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, glycol formal, and diglycol formal. It is an oxymethylene copolymer containing 0.1 to 20% by weight of an alkylene unit. It also includes oxymethylene copolymers having branched molecular chains and oxymethylene block copolymers containing 50% by weight or more of repeating units of oxymethylene and less than 50% by weight of different polymer units.

The multiphase interpolymer (B) used in the present invention comprises a core phase and an outer shell phase, and (a) the core phase comprises acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms. It is a polymer which contains at least one monomer selected from the group consisting of esters as a main component and does not contain a graft polymer, and (b) the outer shell phase comprises acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 4 carbon atoms. It is a multiphase interpolymer which is a polymer containing at least one monomer selected from the group consisting of esters as a main component and not containing a graft polymer.

(A) The polymer constituting the core phase contains as a main component at least one monomer selected from the group consisting of esters of acrylic acid or methacrylic acid and alkyl alcohols having 1 to 12 carbon atoms, and is a graft polymer. It is a polymer containing no. Examples of the ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms include methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, octyl acrylate, ethylhexyl acrylate, dodecyl acrylate, etc. Acrylic acid ester of methacrylic acid ester; methacrylic acid ester such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and hydroxyethyl methacrylate. Of these, butyl acrylate, ethylhexyl acrylate, and methyl methacrylate are preferable.
These acrylic acid esters and methacrylic acid esters may be used alone or in combination of two or more.

In a polymer containing, as a main component, at least one monomer selected from the group consisting of esters of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms, which constitutes the core phase, and does not include a graft polymer. The monomer ratio is not particularly limited, but preferably at least one monomer selected from the group consisting of esters of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms is 50% by weight or more.

The core phase does not have to be one phase as long as the object of the present invention is not impaired, and at least one selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms. The monomers may have different monomer ratios and may be composed of a plurality of polymer phases not including a graft polymer. In addition, a polymer other than a polymer containing at least one monomer selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms as a main component and not including a graft polymer. It may include a phase.

(B) The outer shell phase contains at least one monomer selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 4 carbon atoms as a main component and does not contain a graft polymer. Is. Examples of the ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 4 carbon atoms include acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate; methyl methacrylate, ethyl methacrylate. , Methacrylic acid esters such as butyl methacrylate and hydroxyethyl methacrylate, among which butyl acrylate,
Methyl methacrylate is preferred. These may be used alone or in combination of two or more.

In addition to the above-described monomer composition of the core phase and the shell phase of the multiphase interpolymer used in the present invention, the compositions of the core phase and the shell phase are substantially different. Aromatic vinyl monomers such as styrene, p-methylstyrene, α-methylstyrene, etc. for the core and outer phases of the multiphase interpolymer used in the present invention; vinyl chloride, chloride Vinylidene and other halogenated vinyl monomers; acrylonitrile, methacrylonitrile and other nitrile monomers; vinyl acetate, vinyl propionate and other vinyl esters; acrylamide, methacrylamide and other unsaturated amides, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, etc. Vinyl alkyl ethers; monomers such as diethylene glycol diacrylate, butylene diacrylate, and divinylbenzene that have two or more double bonds in one molecule; conjugated dienes such as butadiene and isoprene; Vinyl monomers having hydroxyl groups such as cyethyl, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxyisopropyl acrylate, hydroxyisopropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate; glycidyl acrylate, methacrylic acid It is also possible to copolymerize glycidyl esters of α, β-unsaturated acids such as glycidyl and glycidyl ethacrylic acid.

It is necessary that the core and outer phases of the multiphase interpolymer used in the present invention do not contain a graft polymer. When a multiphase interpolymer containing a graft polymer is used, only the low level of low gloss, which is the object of the composition of the present invention, can be obtained. The graft polymer is a polymer obtained from a monomer composition containing a grafting monomer having a plurality of unsaturated bonds having different reactivities such as allyl acrylate and allyl methacrylate.

A preferred combination of the polymers constituting the core phase and the outer shell phase of the multiphase interpolymer used in the present invention is, for example, a polymer whose main shell phase is methyl methacrylate, and Polymers whose main core phase is butyl acrylate 60 wt% or more and other copolymerizable monomers 40 wt% or less as main components; Outer shell phase is a polymer whose main component is methyl methacrylate and whose core is Polymer obtained by copolymerizing 50% by weight or more of ethylhexyl acrylate and 50% by weight or less of other copolymerizable monomers; 90% by weight or more of methyl methacrylate and 10% by weight of hydroxyethylene methacrylate in the outer phase. A polymer having the following main components, and the core phase of which is butyl acrylate 60% by weight or more,
Other examples include polymers obtained by copolymerizing 40% by weight or less of other copolymerizable monomers.

The multiphase interpolymer used in the present invention is disclosed in Japanese Patent Publication No. 55-27576 or Japanese Patent Laid-Open No. 59-59.
It can be produced using a conventional emulsion polymerization technique described in JP-A-136343. As a specific production example of the multiphase interpolymer, in the water containing an emulsifier such as sodium dioctylsulfosuccinate, the above-mentioned monomer necessary for forming the core phase and a polymerization initiator such as diisopropylbenzene hydroperoxide are added. Polymerization is carried out at a usual temperature of 50 to 90 ° C. with stirring. At this time, it is preferable to copolymerize a polyfunctional crosslinking agent such as a divinyl compound in order to impart appropriate elasticity to the core phase. The amount of the polyfunctional crosslinking agent added is preferably 0.1 to 5.0% by weight based on the total weight of the polymer forming the core phase.

At the time when the polymerization reaction forming the core phase is completed, next, the monomer forming the outer shell phase is additionally added. At this time, a polymerization initiator can be additionally added. The multiphase polymer obtained by the emulsion polymerization can be separated from water while maintaining the particle form by using a conventional means such as salting out, freeze-thawing, or spray drying.

The particle size of the multiphase interpolymer is preferably 1 μm or less from the viewpoint of low gloss. The optimum particle size is 0.05 μm to 0.5 μm. The compounding amount of the multiphase interpolymer used in the present invention is 1 to 50% by weight. This is because if the amount is less than 1% by weight, these addition effects do not appear for low gloss, and if the amount exceeds 50% by weight, the moldability and mechanical properties of the polyoxymethylene resin are significantly deteriorated. Among them, the preferable range for maximizing the effect of the present invention is 2 to 20% by weight, and the most preferable range is 4 to 15% by weight.

As the multiphase interpolymer, one having a small content of alkali metal and sulfur compound is used. The alkali metal and the sulfur compound in the present invention include sulfonates such as lithium dodecylbenzene sulfonate, soda, and potassium used in the production of multiphase interpolymers, lithium lauryl sulfate, soda, and potassium. This is due to an emulsifier such as a sulfate ester salt and a salting-out agent such as sodium sulfate and sodium chloride.

That is, the alkali metal in the present invention means lithium, potassium and sodium. The content of the alkali metal in the multiphase interpolymer can be quantified by a general method, among which atomic absorption or plasma emission method can be used. In the present invention, quantification was performed using the atomic absorption method. That is, this is a method of subjecting the multiphase interpolymer to carbonization or ashing, and extracting the alkali metal content from it with an aqueous acid solution and subjecting it to atomic absorption.

The content of the alkali metal in the present invention is the total of the alkali metals (lithium, potassium, sodium) analyzed by the atomic absorption method, and is preferably 100 ppm or less with respect to the multiphase interpolymer. More preferably 80 ppm or less, most preferably 60
It is below ppm. The sulfur content in the multiphase interpolymer can be quantified by a general method, of which the ion chromatography method is preferable. In the present invention, this ion chromatography method was used for quantification. That is, it is a method in which a multiphase interpolymer is burned by a flask burning method, and a liquid obtained by extracting a sulfur content with an alkaline aqueous solution is subjected to ion chromatography.

The sulfur content in the present invention is calculated by converting the total amount of sulfur compounds analyzed by ion chromatography into the amount of elemental sulfur, and is preferably 200 ppm or less based on the multiphase interpolymer. More preferably 150 ppm or less, most preferably 100 p
It is pm or less. The composition of the present invention comprises a polyoxymethylene resin and a multiphase interpolymer, a blend,
Further, it can be obtained by melt-kneading.

Examples of the melt kneader include a kneader,
Although a known device such as a roll mill or an extruder which is usually used for kneading a resin melt can be used, the extruder is most suitable from the viewpoints of blocking oxygen and working environment. Types of this extruder include uniaxial type, biaxial type, vented type, and no vent type, and the composition of the present invention can be prepared by any type of extruder.

The composition contains antioxidants, light stabilizers, ultraviolet absorbers, lubricants, impact modifiers, crystal nucleating agents, antistatic agents, inorganic fillers, pigments which are usually added to plastics. Etc. can be added as needed.
In addition, polyamide, melamine, melamine derivatives, dicyandiamide, which are usually added to polyoxymethylene resins,
Fatty acid calcium and the like can also be added.

Particularly, as the antioxidant, 3-methyl-
Antioxidants having a 4-hydroxy-5-t-butylphenyl group are preferred. This is because, when this antioxidant is added at the same time, the retention coloring is surprisingly improved as compared with other antioxidants. As a specific antioxidant, for example,
3,9-bis [2- [3- (t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,
1-dimethylethyl-2,4,8,10-tetraoxaspiro [5,5] undecane, triethyleneglycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3-t-butyl-5-methyl-
4-hydroxyphenyl) propionate], pentaerythritol-tetrakis [3- (3-t-butyl-5]
-Methyl-4-hydroxyphenyl) propionate], octadecyl-3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate, N, N
-Hexamethylene bis- (3-t-butyl-5-methyl-4-hydroxy-hydrocinnamamide) and the like.

The preferred antioxidant is 3,9-bis [2-
[3- (t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl-2,4,8,10-tetraoxaspiro [5,5] undecane, triethyleneglycol- Bis [3- (3-
t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3
-(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate].

As the light stabilizer, bis (2,2,6,6)
-Tetramethylpiperidyl) sebacate, bis (2,
A hindered amine light stabilizer such as 2,6,6-tetramethylpiperidyl) adipate can be used. As an ultraviolet absorber, 2- [2'-hydroxy-3 ', 5'-
Benzotriazole-based UV absorbers such as bis- (α, α-dimethylbenzyl) phenyl] benzotriazole and 2- (2′-hydroxy-5′-methyl-phenyl) benzotriazole can be used.

The polyoxymethylene resin composition having excellent low gloss of the present invention can be used as a blend with generally used polyoxymethylene homopolymers, copolymers, branched polymers and block copolymers. The polyoxymethylene resin composition in the present invention imparts effective low gloss to a molded article of any surface, but particularly to a molded article molded with a textured mold. Exhibits a large low gloss effect.

Preferable uses of the polyoxymethylene resin composition of the present invention are, for example, levers, instrumental panels, switch parts, handles, clips, housings and the like. Especially suitable for automobile interior parts.

[0032]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

[0033]

Reference Example 1 <Production of Polyoxymethylene Resin> A polyoxymethylene copolymer containing 2.8% ethylene oxide was prepared in US Pat.
Polymerization was carried out by a known method described in 0237352. The polymer had an intrinsic viscosity of 1.1 (2% by weight
0.1% by weight of the polymer was dissolved in a p-chlorophenol solution containing α-pinene of Example 1 and measured at 60 ° C). Further, the melt index according to ASTM D1238 (condition E) was 10.0 g / 10 minutes. This polyoxymethylene polymer is designated as P-1.

Both ends acetylated polyoxymethylene homopolymer powder was prepared by a known method in US Pat. No. 2,998,409. This had an intrinsic viscosity of 1.2 and a melt index of 9.0 g / 10 minutes. This polyoxymethylene polymer is designated as P-2.

[0035]

[Reference Example 2] <Production of multi-phase interpolymer> 5.7 liters of distilled water was added to a 10 liter beaker equipped with a stirrer and a condenser, and sodium dioctylsulfosuccinate 2 was used as an emulsifier.
0 g and Rongalit 1.2 g as a reducing agent are added and uniformly dissolved.

As the core phase of the first phase, a homopolymer solution of 2 g of the monomer composition shown in the attached table and diisopropylbenzene hydroperoxide (hereinafter abbreviated as PBP) was added and polymerized at 80 ° C. The polymerization yield at this point was almost 100%. Next, as the outer shell phase of the second phase, the monomer composition described in the attached table, PBP 0.6 g, and n-octyl mercaptan 0.2
g homogeneous solution was added.

The yield of the reaction at this stage was almost 100%. The temperature was then raised to 95 ° C and held for 1 hour.
The obtained polymer is put into a 0.5% aluminum chloride aqueous solution to coagulate the polymer, and washed with warm water 5 to 15 times,
After drying, various multiphase interpolymers in the form of white flocs were obtained. The average particle size of the obtained multiphase interpolymer was 0.1 to 0.5 μm. In addition, respective alkali metal contents and sulfur contents are shown in Tables 1 to 3.

[0038]

Examples 1 to 13 and Comparative Examples 1 to 6 <Production of Polyoxymethylene Resin Composition> The above polyoxymethylene resin and the multiphase interpolymer were blended at the compounding ratios shown in Tables 1 to 3 to form a cylinder. The temperature is 2
Melt kneading with a twin-screw vented extruder set at 00 ° C,
The resulting composition was pelletized. <Evaluation of Composition> The final pellets obtained were molded with a 3 ounce molding machine to obtain test pieces. Evaluate this by the following method,
The results are shown in Tables 1 to 3.

Gloss: Measured with a gloss meter manufactured by Nippon Denshoku Industries Co., Ltd. at an incident angle of 60 ° and a reflection angle of 60 °. Tensile strength, tensile elongation: according to ASTM D638. Flexural strength; flexural modulus: according to ASTM D790. Izod value: According to ASTM D256. Thermal stability: The final pellets obtained have a cylinder temperature of 22.
When molding the above-mentioned test piece with a 3 ounce molding machine set at 0 ° C., the critical residence time (minute) until the occurrence of silver streak in the test piece was measured.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

According to the present invention, the core phase contains at least one monomer selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms as a main component, and a graft polymer. A polymer containing no at least one monomer selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 4 carbon atoms as a main component,
A polyoxymethylene resin composition excellent in both low gloss and mechanical properties by blending a polyoxymethylene resin with a multi-phase interpolymer that is a polymer that does not contain a graft polymer and is different from the core phase Can be obtained.

Claims (1)

[Claims] 1. A polyoxymethylene resin (A) 50 to 9
9% by weight and (B) a core phase and an outer shell phase, and (a) the core phase is at least one selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 12 carbon atoms. It is a polymer containing a monomer as a main component and not a graft polymer, and (b) the outer shell phase is at least one selected from the group consisting of an ester of acrylic acid or methacrylic acid and an alkyl alcohol having 1 to 4 carbon atoms. A low gloss polyoxymethylene resin composition comprising a monomer as a main component and a multiphase interpolymer, which is a polymer not containing a graft polymer, in an amount of 1 to 50% by weight.