JPH06293856A - Polyacetal resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition which contains a prescribed amount of a specific aliphatic ester and is suitable for molded parts such as ink-jet head for printers because it has excellent leakage properties without any adverse effect on moldability and mechanical properties. CONSTITUTION:This resin composition contains 0.01 to 10wt.% of a fatty acid ester between an aliphatic acid of more than 10 carbon atoms such as capric acid and an ether formed by dimerized or more polymerized of a 3 or more hydric alcohol such as glycerol. The melt index of the composition (ASTM-D 1238-89, method E) is less than 2 and the contact angle of the formed products is less than 50 deg.C.

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 water, an aqueous ink, an aqueous solution such as serum.

[0002]

2. Description of the Related Art As is well known, polyacetal resin is an engineering material which has excellent physical properties such as mechanical properties and electrical properties, or chemical properties such as chemical resistance and heat resistance. Recently, it has been used as a resin in a very wide range of fields. However,
With the expansion of fields in which polyacetal resins are used, the properties of the materials may require more specificity. As one of such peculiarities, further improvement of wettability is demanded. Wettability is, for example, JI
As shown in S K6768, it is determined that the liquid applied to the solid surface wets the non-repellent state. Further, as a method often used, there is measurement of a contact angle. The contact angle has a relation expressed by Young's equation between the surface tension and the interfacial tension of the solid and liquid forming the contact angle, and when the contact angle is θ, it is represented by cos θ = 2Wa / Wc-1. Thus, the work Wa of the adhesion of the solid to the liquid and the work Wc of the aggregation of the liquid are determined by the balance. That is, it is judged that the smaller the contact angle, the larger the work of adhesion of the solid to the liquid and the easier the wetting. There are various molded products that require wettability, for example, in an inkjet head used in a printer for a personal computer, in order to make the ink flight direction constant and improve the print quality,
It is necessary to improve the wetting characteristics of the ink nozzle end surface. Further, it is necessary for the carrier of the biosensor to improve the wetting property of the liquid to be measured in order to improve the measurement sensitivity. Generally, plasma treatment, chemical treatment, and surface coating with a coating agent are performed to improve wetting characteristics, but high control technology is required to ensure the uniformity of the treated surface, and process efficiency deterioration cannot be avoided. . On the other hand, as a technique for improving the wetting property of the polyacetal resin, there is a method of blending an additive for improving the wetting property, for example, polyethylene glycol (JP-A-4-257499). But,
It is insufficient to meet various requirements, and even if the required level is relatively low, a large amount of addition is required, which may adversely affect mechanical properties and moldability. Therefore, an additive that can obtain a sufficient wetting property even when added in a small amount has been desired.

[0003]

DISCLOSURE OF THE INVENTION As a result of intensive studies in view of the above problems of the prior art, the present inventors have found that a sufficient amount of wetting property can be obtained by adding a small amount of a specific compound. More specifically, by blending a polyacetal with a fatty acid ester of an ether in which two or more polyhydric alcohols having three or more hydroxyl groups are bonded to polyacetal, sufficient wetting properties can be obtained without changing the moldability and mechanical properties. The present invention has been completed and the present invention has been completed. That is, the present invention is a polyacetal resin composition containing 0.01 to 10% by weight of a fatty acid ester of an ether in which two or more polyhydric alcohols having 3 or more hydroxyl groups are bonded.

The ester having the characteristics of the present invention is a compound in which a fatty acid is ester-bonded to an ether in which two or more polyhydric alcohols having three or more hydroxyl groups are bonded. A simple polyalkylene glycol or a fatty acid ester of a polyhydric alcohol, although its cause is unknown, does not provide sufficient wetting characteristics as shown in Comparative Examples below. It was found that wettability can be significantly improved by using a polyhydric alcohol ether and a fatty acid ester having 3 or more hydroxyl groups, that is, a fatty acid ester of a polyhydric alcohol ether in which hydroxyl groups not involved in the bond remain. That is the feature of the present invention.

Ethers of polyhydric alcohols having 3 or more hydroxyl groups, which are constituents of the ester used in the present invention, are, for example, diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, heptaglycerin, octaglycerin. , Nonaglycerin, decaglycerin, undecaglycerin, dodecaglycerin, tridecaglycerin, dierythritol, trierythritol, tetraerythritol, pentaerythritol, hexaerythritol, heptaerythritol,
Octaerythritol, Nonaerythritol, Decaerythritol, Undecaerythritol, Dodecaerythritol, Tridecaerythritol, Dimannitol, Trimannitol, Tetramannitol, Pentamannitol, Hexamannitol, Heptamannitol, Octamannitol, Nonamannitol, Decamannitol, Undecamannitol. , Dodecamannitol, tridecamannitol, disorbitol, trisorbitol, tetrasorbitol, pentasorbitol, hexasorbitol, heptasorbitol, octasorbitol, nonasorbitol, decasorbitol, undecasorbitol, dodecasorbitol, tridecasorbitol and the like. , Preferably diglycerin, triglycerin, tetrag Serine, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol, decaglycerol, undecalactone glycerin, dodecamethylene glycerin, polyglycerin, such as avian decaglycerol. The fatty acid which is a constituent component of the ester preferably has 10 or more carbon atoms. Carbon number
If it is less than 10, the effect of improving the wetting property may not be sufficiently obtained. The fatty acid having 10 or more carbon atoms, for example, capric acid, undecyl acid, lauric acid, tridecyl acid,
Myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachidic acid,
Examples thereof include behenic acid, lignoceric acid, cerotic acid, undecylenic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid. Preferred are lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid and the like. The amount of the ester used in the present invention is 0.01 to 10% by weight, preferably 0.1 to 5% by weight.
Is. If the addition amount is less than 0.01% by weight, the effect of improving the wettability is not exerted, and if the addition amount exceeds 10% by weight, mechanical properties and melt viscosity may decrease. The decrease in melt viscosity often narrows the range of conditions for extrusion molding, leading to deterioration in extrusion moldability, which is not preferable. The melt index (ASTM
D1238-89, Method E) 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 Examples of less than 50 degrees. It is of course possible to use a mixture of two or more compounds within the scope of the present invention.

The polyacetal resin used in the present invention is a polymer 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. The copolymer may be a terpolymer or a block copolymer, and the molecule may have not only a linear structure but also a branched or crosslinked structure. The degree of polymerization is not particularly limited, but the melt index of the composition is preferably 2 or less as described above.

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

The composition of the present invention can be prepared by the equipment and method generally known as a method for preparing a synthetic resin composition. That is, the necessary components can be mixed, kneaded using a uniaxial or biaxial extruder, extruded into pellets for molding, and then molded, or the composition can be molded by a molding machine. It is also possible to do it at the same time. Further, in order to improve the dispersion and mixing of the respective components, a method of crushing a part or all of the resin components, mixing and molding the pellets melt-extruded, etc. are all possible. In addition, the compounds such as the stabilizers and additives may be added at any arbitrary stage, and it is of course possible to add and mix them immediately before obtaining the final molded product. 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 particularly in the case of extrusion molding, the effect of the present invention is remarkable. 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. [Wetability] Using the pellets of the compositions prepared in Examples and Comparative Examples, a plate of 30 mm × 50 mm × 3 mm was formed by an injection molding machine, and one drop of water was dropped on the plate to form a plate surface. The angle formed by the tangent line drawn from the contact point between the water droplet and the plate to the water droplet surface, that is, the contact angle (θ) was measured (see FIG. 1). An automatic contact angle meter CA-Z type manufactured by Kyowa Interface Science Co., Ltd. was used for the measurement. The smaller the contact angle, the better the wetting property, but it is judged that the contact angle is less than 50 degrees is very excellent. [Tensile Strength] Using the pellets of the compositions prepared in Examples and Comparative Examples, ASTM No. 4 dumbbell test pieces were molded by 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
(° C, load: 2.16 kg) Examples 1 to 4 and Comparative Examples 1 to 5 As shown in Table 1, polyacetal resin [manufactured by Polyplastics, trade name "Duracon (U10)", various additives shown in Table 1 were added. After mixing, they were melt-kneaded using a 30 mm twin-screw extruder to prepare pelletized compositions. Then, a test piece was molded from the pellet using an injection molding machine, and the wetting property and other properties were measured and evaluated. The results are also shown in Table 1.

[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 is obtained by blending a polyacetal resin with a fatty acid ester of an ether in which two or more polyhydric alcohols having three or more hydroxyl groups are bonded. Compared to a composition that does not use these components, shows a sufficient wetting property with a small addition amount, since there is little decrease in mechanical properties and no decrease in melt viscosity, a molding material that requires wetting properties,
It is particularly suitable as a material for extrusion molding. Therefore, the polyacetal resin composition of the present invention is a molded part of any field requiring wettability, that is, an inkjet head for printers, a biosensor carrier, an offset printing plate, an ink reservoir of a writing instrument, an ink derivative and a nib, a printing metal. It can be suitably used for coating and the like.

[Brief description of 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 (5)

[Claims] 1. A fatty acid ester of an ether having two or more polyhydric alcohols having three or more hydroxyl groups bonded to each other is 0.01 to
A polyacetal resin composition containing 10% by weight. 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 polyacetal resin composition according to claim 1, wherein the polyhydric alcohol constituting the fatty acid ester is glycerin. 4. The melt index of the composition (ASTM D12
38-89, E method) is 2 or less.
The polyacetal resin composition according to the item. 5. The polyacetal resin composition according to claim 1, wherein the molded product of the composition has a contact angle of less than 50 degrees.