JP3203281B2 - Polyacetal resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyacetal resin composition capable of easily obtaining a molded article surface having improved wettability with an aqueous solution such as water, an aqueous ink or serum.

[0002]

2. Description of the Related Art As is well known, polyacetal resin is an engineering material having excellent physical properties such as mechanical properties and electrical properties, or chemical properties such as chemical resistance and heat resistance. In recent years, it has been used in a very wide field as a resin. However,
With the expansion of the field in which polyacetal resins are used, there may be cases where properties as materials are required to be more specific. As one of such specialties, further improvement in wettability is demanded. The wettability is, for example, JI
As shown in SK 6768, it is determined that the liquid applied to the solid surface wets a state that is not repelled. Also, there is a method of measuring a contact angle as a frequently used method. The contact angle has a relationship expressed by the Young's equation between the surface tension and the interfacial tension of the solid and liquid forming the contact angle. When the contact angle is θ, it is expressed by cos θ = 2Wa / Wc−1. Thus, it is determined by the balance between the work of attaching Wa to the solid liquid and the work of coagulating the liquid Wc. That is, it is determined that the smaller the contact angle is, the larger the work of adhering to the solid liquid is, and the easier it is to get wet. There are various molded products that require wettability, for example, in an ink jet head used in a printer for a personal computer, in order to maintain a constant ink flight direction and improve print quality,
It is necessary to improve the wetting characteristics of the ink nozzle end surface. In addition, it is necessary for the carrier of the biosensor to improve the wettability of the liquid to be measured in order to improve the measurement sensitivity. Generally, plasma treatment, chemical treatment, surface coating with a coating agent, etc. are performed to improve the wetting characteristics, but high control technology is required to ensure uniformity of the treated surface, and deterioration of process efficiency is inevitable. . On the other hand, as a technique for improving the wetting characteristics of a polyacetal resin, there is a method of blending an additive for improving the wetting characteristics, for example, polyethylene glycol (JP-A-4-257499). But,
It is not sufficient to meet various requirements, and even when the required level is relatively low, a large amount of addition is required, which may adversely affect mechanical properties and moldability. Therefore, an additive capable of obtaining sufficient wetting properties with a small amount of addition has been desired.

[0003]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned problems of the prior art and found that sufficient wetting characteristics can be obtained by adding a small amount of a specific compound. More specifically, by compounding the polyacetal with a polyalkylene glycol adduct of a fatty acid ester of a polyhydric alcohol and having a remaining hydroxyl group, sufficient wettability can be obtained without changing the moldability and mechanical properties. And found that the present invention was completed. That is, the present invention is a polyacetal resin composition containing 0.01 to 10% by weight of a polyalkylene glycol adduct of a polyhydric alcohol and a compound having a remaining hydroxyl group.

The polyalkylene glycol adduct of an ester (hereinafter abbreviated as a PAG adduct of an ester), which is a feature of the present invention, is obtained by adding a polyalkylene glycol to a fatty acid ester of a polyhydric alcohol and remaining a hydroxyl group. Compound. In simple polyalkylene glycol or fatty acid ester of polyalkylene glycol,
Although the cause is unknown, sufficient wettability cannot be obtained as shown in Comparative Examples below. It is a feature of the present invention to use a compound in which the hydroxyl group remains except for the terminal hydroxyl group of the polyalkylene glycol. The polyhydric alcohol constituting the PAG adduct of the ester used in the present invention is a compound in which three or more hydroxyl groups are present in order for the hydroxyl group to remain after the formation of the PAG adduct of the fatty acid ester. Examples of the polyhydric alcohol include glycerin, erythritol, mannitol, sorbitol and the like, and preferably glycerin. The fatty acid constituting the PAG adduct of the ester preferably has 10 or more carbon atoms. If the number of carbon atoms is less than 10, the effect of improving the wetting characteristics may not be sufficiently obtained. As fatty acids having 10 or more carbon atoms, for example, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid Cerotic acid, undecylenic acid, oleic acid, elaidic acid, setrenic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and the like.
Preferred are lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid and the like. The polyalkylene glycol which is a component of the PAG adduct of the ester used in the present invention includes polyethylene glycol,
Polypropylene glycol, polybutylene glycol,
Polypentamethylene glycol, polyhexamethylene glycol, polyheptamethylene glycol, polyoctamethylene glycol, polynonamethylene glycol, polydecamethylene glycol, etc. are preferred, but polyethylene glycol is preferred. The molecular weight of the polyalkylene glycol is preferably 200 or more, more preferably 500
That is all. If the molecular weight is less than 200, the effect of improving the wetting properties may be low. The addition amount of the PAG adduct of such an ester is 0.0110% by weight, more preferably 0.1 to 5% by weight, based on the polyacetal resin. The amount added is 0.
If it is less than 01% by weight, the effect of improving the wettability is not exhibited, and if it exceeds 10% by weight, the mechanical properties and the melt viscosity may be reduced. A decrease in melt viscosity often narrows the range of conditions for extrusion molding, which leads to deterioration of extrudability, which is not preferable. As a measure of the melt viscosity of a preferred composition, a melt index (ASTM D1238-89, method E) is used.
Is 2 or less, more preferably 1.5 or less. Particularly preferred is a composition having a contact angle of the molded article of the composition measured by the method described in the Examples of less than 50 degrees. Of course, two or more compounds can be used in combination as long as they are compounds within the scope of the present invention.

The polyacetal resin used in the present invention is a high molecular compound having an oxymethylene group (—CH ₂ O—) as a main constituent unit, and contains a small amount of other constituent units in addition to the polyoxymethylene homopolymer and the oxymethylene group. May be any of a copolymer, a terpolymer and a block copolymer, and the molecule may have not only a linear but also a branched or crosslinked structure. The degree of polymerization is not particularly limited, but preferably, the composition has a melt index of 2 or less as described above.

In order to impart desired properties to the composition of the present invention, conventionally known additives such as stabilizers, lubricants, nucleating agents, mold release agents, or organic polymer materials, inorganic or organic It is also possible to add and contain one or more of fibrous, powdery and plate-like fillers.

The composition of the present invention can be prepared by equipment and a method generally known as a method for preparing a synthetic resin composition. That is, necessary components can be mixed, kneaded using a single-screw or twin-screw extruder, extruded to form pellets for molding, and then molded. It can be done at the same time. Also, to improve the dispersion and mixing of each component, crush some or all of the resin components,
Any method such as a method of forming pellets which are mixed and melt-extruded is possible. The compounds such as the stabilizers and additives may be added at any arbitrary stage, and may be added or mixed immediately before obtaining a final molded article. Also,
The resin composition according to the present invention can be molded by any of extrusion molding, injection molding, compression molding, vacuum molding, blow molding, and foam molding, and the effect of the present invention is particularly remarkable in the case of extrusion molding.

[0008]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. still,
The methods used for evaluating the characteristic values such as the wetting characteristics in the examples are as follows. [Wet property] Using a pellet of the composition prepared in Examples and Comparative Examples, a 30 mm x 50 mm x 3 mm plate was molded by an injection molding machine, and a drop of water was dropped on this plate. The angle formed by a tangent drawn from the contact point between the water droplet and the plate to the surface of the water droplet, that is, the contact angle (θ) was measured (see FIG. 1). An automatic contact angle meter CA-Z manufactured by Kyowa Interface Science Co., Ltd. was used for the measurement. The smaller the contact angle is, the better the wetting property is, but it is judged that the contact angle is particularly excellent when the contact angle is less than 50 degrees.

[Tensile Strength] A test piece of ASTM No. 4 dumbbell was molded from the pellets of the compositions prepared in Examples and Comparative Examples using an injection molding machine, and the tensile strength was measured in accordance with ASTM D638.

[Melt index] ASTM D1238-89,
The melt index was measured according to the E method. (Barrel temperature: 190 ° C., load: 2.16 kg) Examples 1 to 4 and Comparative Examples 1 to 6 As shown in Table 1, polyacetal resin [manufactured by Polyplastics, trade name “Duracon (U10)”; After mixing the various additives shown, the mixture was melt-kneaded using a 30 mm twin screw extruder to prepare a pellet-shaped composition. Next, test pieces were molded from the pellets using an injection molding machine, and the wettability and other properties were measured and evaluated. The results are shown in Table 1.

[0011]

[Table 1]

Note) A-1: Polyethylene glycol adduct of glycerin monostearate (molecular weight of polyethylene glycol about 900) A-2: Polypropylene glycol adduct of glycerin monostearate (molecular weight of polypropylene glycol about 1000) A-3 : Polyethylene glycol adduct of glycerin monobehenate (molecular weight of polyethylene glycol of about 150
0) B: polyethylene glycol monostearate C: glycerin monostearate D: polyethylene glycol (molecular weight about 1000) E: polyethylene glycol (molecular weight about 6000)

[0013]

As is apparent from the above description and Examples, the composition of the present invention comprising a polyacetal resin and a compound obtained by adding a polyalkylene glycol to a fatty acid ester of a polyhydric alcohol, comprises these components. Compared to compositions not used, it shows sufficient wetting characteristics with a small amount of addition, and since there is little decrease in mechanical properties and no decrease in melt viscosity, it is used as a molding material requiring wetting characteristics, especially as a material for extrusion molding. It is suitable. Therefore, the polyacetal resin composition of the present invention can be used for molded parts in all fields requiring wettability, such as ink jet heads for printers, biosensor carriers, offset printing plates, ink reservoirs and ink derivatives for writing instruments and nibs, and metal for printing. It can be suitably used for coating and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a measurement state of a contact angle (θ) in a wetting property evaluation test performed in an example.

Claims (6)

(57) [Claims] 1. A polyacetal resin composition comprising a polyalkylene glycol adduct of a fatty acid ester of a polyhydric alcohol and containing 0.01 to 10% by weight of a compound having a remaining hydroxyl group. 2. The polyacetal resin composition according to claim 1, wherein the fatty acid constituting the fatty acid ester of the polyhydric alcohol has 10 or more carbon atoms. 3. The polyacetal resin composition according to claim 1, wherein the polyalkylene glycol added to the fatty acid ester of the polyhydric alcohol is polyethylene glycol. 4. The polyacetal resin composition according to claim 1, wherein the polyhydric alcohol constituting the polyhydric alcohol fatty acid ester is glycerin. 5. The melt index (ASTM D12) of the composition.
38-89, Method E) is 2 or less.
Item 7. The polyacetal resin composition according to Item 1. 6. The polyacetal resin composition according to claim 1, wherein a contact angle of the composition molded product is less than 50 degrees.