JP3260006B2 - 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 S K6768, 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 mixing a fatty acid ester of a specific ether, in which two or more polyhydric alcohols having 3 or more hydroxyl groups are bonded, into polyacetal, sufficient wettability can be obtained without changing molding processability and mechanical properties. And found that the present invention was completed. That is, the present invention relates to polyglycerin (excluding diglycerin)
A polyacetal resin composition comprising a fatty acid ester of 0.01 to 10% by weight and having a molded product having a contact angle of less than 50 degrees.

[0004] Esters having the characteristics of the present invention are compounds in which a fatty acid is ester-bonded to a specific ether in which two or more polyhydric alcohols having 3 or more hydroxyl groups are bonded. With simple polyalkylene glycols or fatty acid esters of polyhydric alcohols, the cause is unknown, but sufficient wettability cannot be obtained as shown in Comparative Examples below. Polyhydric alcohol ethers having 3 or more hydroxyl groups and esters of fatty acids, that is, polyhydric alcohol ethers (excluding diglycerin, excluding diglycerin , in which hydroxyl groups not participating in bonding remain).
It is a feature of the present invention that the wettability can be significantly improved by using the fatty acid ester of (1) .

[0005] ethers of polyhydric alcohols hydroxyl number which is a component is 3 or more of the present invention to ester used, for example, Application Benefits glycerin, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol,
Octaglycerin, nonaglycerin, decaglycerin,
Undecalactone glycerin, dodecamethylene glycerin, polyglycerin such as Toridekaguri <br/> serine.

[0006] The polyacetal resin used in the present invention is a high molecular compound having an oxymethylene group (-CH ₂ O-) as a main structural unit and contains a small amount of other structural units other than polyoxymethylene homopolymer and 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 further impart desired properties to the composition of the present invention, conventionally known additives such as stabilizers, lubricants, nucleating agents, 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. Further, in order to improve the dispersion and mixing of the components, a method of pulverizing a part or all of the resin component, mixing the resultant, and forming a melt-extruded pellet may be used. 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. Further, 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. is there.

[0009]

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] Using the pellets of the compositions prepared in Examples and Comparative Examples, an ASTM No. 4 dumbbell test piece was molded using an injection molding machine, and the tensile strength was measured according to ASTM D638. [Melt Index] The melt index was measured according to ASTM D1238-89, Method E. (Barrel temperature: 190
Examples 1 to 4 and Comparative Examples 1 to 5 As shown in Table 1, a polyacetal resin (manufactured by Polyplastics, trade name "Duracon (U10)" was mixed with various additives shown in Table 1). After mixing, 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. Table 1 also shows the results.

[0010]

[Table 1]

Note) A-1: decaglycerin monolaurate A-2: decaglycerin monostearate A-3: octaglycerin monolaurate B: glycerin monolaurate C: polyethylene glycol (molecular weight 1000) D: polyethylene glycol (Molecular weight 6000)

[0012]

As is apparent from the above description and Examples, the composition of the present invention obtained by mixing a polyacetal resin with a fatty acid ester of an ether having two or more polyhydric alcohols having 3 or more hydroxyl groups bonded thereto. Shows a sufficient wetting property with a small amount of addition compared to a composition not using these components, and since there is little decrease in mechanical properties and no decrease in melt viscosity, a molding material requiring wetting properties,
Particularly, it is suitable as a material for extrusion molding. 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 (3)

(57) [Claims] 1. Polyglycerin (excluding diglycerin )
G) containing 0.01 to 10% by weight of a fatty acid ester,
A polyacetal resin composition having a contact angle of a molded article of less than 50 degrees. 2. The polyacetal resin composition according to claim 1, wherein the fatty acid constituting the fatty acid ester has 10 or more carbon atoms. 3. The melt index of the composition (ASTM D12
38-89, Method E) is 2 or less.