JPH04298572A - Colorant for polyacetal and production of colored polycetal - Google Patents

Abstract

PURPOSE:To prepare the title colorant which disperses well in polyacetal without causing thermal decomposition thereof by compounding a pigment with a dispersant comprising a hydroxylated fatty acid ester of a polyhydric alcohol. CONSTITUTION:The title colorant contains, as essential components, a pigment and a dispersant comprising a hydroxylated fatty acid ester of a polyhydric alcohol. The ester prepd. by the esterification of a hydroxylated fatty acid with a polyhydric alcohol, esp. glycerin, is pref. A glyceride which is solid at room temp. and hardly bleeds out from polyacetal is esp. pref. because it can easily be mixed with the pigment, an example being 12-hydroxystearic acid triglyceride.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colorant for polyacetal and a method for producing colored polyacetal using the colorant.

0002

BACKGROUND OF THE INVENTION Conventionally, pigments and dyes have been used to color thermoplastic resins, but many dyes have drawbacks such as color migration and light resistance, so pigments have been mainly used.

[0003] Pigments are granular substances with a size of 0.1 to several tens of micrometers, and are kneaded and added to a molten resin to create the desired coloring state, but if the pigment particles aggregate, this cannot be obtained, and the resin The appearance of the molded product lacks beauty, and sometimes its mechanical strength may be impaired. Therefore, in order to prevent agglomeration of pigment particles and achieve a good dispersion state, dispersed pigments that use metal salts of higher fatty acids or amides as pigment dispersants are generally used, such as general-purpose pigments such as olefin, styrene, and acrylic. Used in resin.

0004

[Problems to be Solved by the Invention] However, when attempting to knead the above-mentioned dispersed pigment into polyacetal, which is an engineering resin, there was a drawback that the polyacetal could not be uniformly colored due to the poor dispersibility of the pigment. On the other hand, pigment dispersants with excellent dispersibility have the drawback of reducing the heat resistance of polyacetal itself.

In particular, when the heat resistance of polyacetal decreases,
When polyacetal and pigment are melt-kneaded, a pungent odor of formaldehyde, which is a thermal decomposition product, is generated, which makes molding work difficult and impairs the mechanical strength of the resin molded product.

An object of the present invention is to provide a coloring agent for polyacetal that causes less thermal decomposition of polyacetal and good pigment dispersion, and to provide a polyacetal colored with the colorant.

[0007]

[Means for Solving the Problems] The inventors of the present invention have made extensive studies in view of the above-mentioned circumstances, and have found that if a polyhydric alcohol fatty acid ester having a hydroxyl group is used as a pigment dispersant, polyacetal can be formed without thermally decomposing the polyacetal. The present inventors have discovered that the dispersibility of pigments can also be solved, and have completed the present invention.

That is, the present invention provides a coloring agent for polyacetal containing a pigment and a pigment dispersant as essential components, characterized in that a polyhydric alcohol fatty acid ester having a hydroxyl group is used as the pigment dispersant. The object of the present invention is to provide a method for producing a colored polyacetal by melt-kneading a polyhydric alcohol fatty acid ester having a hydroxyl group and a polyacetal.

The polyacetal according to the present invention refers to a homopolymer or copolymer of an aldehyde compound, and any known and commonly used polyacetal can be used. Examples of aldehyde compounds include formaldehyde, trioxane, 1,3
-dioxane, etc.

Examples of such polyacetals include homopolymers having oxymethylene as the main structure, trioxane-ethylene oxide copolymers, trioxane-1,
Examples include copolymers in which a part of the main chain is replaced with another structure, such as a 3-dioxane copolymer.

The method for producing polyacetal is not particularly limited, but for example, formaldehyde is polymerized as an essential component in the presence of an anionic polymerization catalyst if necessary, or trioxane is polymerized as an essential component in the presence of a cationic polymerization catalyst if necessary. A common method is to carry out lower polymerization.

As the pigment used in the present invention, any of the conventionally known inorganic pigments, organic pigments and extender pigments can be used. Pigments according to the present invention include, for example, inorganic pigments such as carbon black, titanium oxide, Bengara, ultramarine, cobalt aluminate, and other calcined pigments, phthalocyanine-based, perylene-based, anthraquinone-based, quinacridone-based, isoindolinone-based, and inorganic pigments. Examples include organic pigments such as danthrene-based and azo-based pigments, and extender pigments such as calcium carbonate, barium sulfate, talc, clay, and silica. Among the pigments, those that do not decompose or discolor during the molding process of polyacetal are preferred.

As the polyhydric alcohol fatty acid ester having a hydroxyl group according to the present invention, any known and commonly used ones can be used. Examples of such substances include glycerin monopalmitate, monopentaerythritol palmitate ester, monodiglycerin palmitate ester, monosorbitol myristate ester, glycerin dimyristate, glycerin trimyristate, glycerin monolaurate, and glycerin dilaurate. , glycerin trilaurate, glycerin monostearate,
Fatty acid polyhydric alcohol esters such as glycerin distearate and glycerin tristearate, hydroxyl group-containing compounds such as hydroxypalmitic acid monoglyceride, hydroxymyristic acid monoglyceride, hydroxylauric acid diglyceride, hydroxystearic acid monoglyceride, hydroxystearic acid diglyceride, hydroxystearic acid triglyceride, etc. Examples include polyhydric alcohol esters of fatty acids.

[0014] Compared to polyhydric alcohol esters of fatty acids, polyhydric alcohol fatty acid esters having hydroxyl groups are polyhydric alcohol esters of hydroxyl group-containing fatty acids, that is, the carboxyl group of the hydroxyl group-containing fatty acid and the hydroxyl group of the polyhydric alcohol form an ester bond. Compounds with a bonded structure are more preferable. This indicates that the hydroxyl groups of the hydroxyl group-containing fatty acid contribute more to pigment dispersibility than the residual hydroxyl groups of the polyhydric alcohol.

[0015] As the polyhydric alcohol fatty acid ester having a hydroxyl group according to the present invention, a glycerin ester of a hydroxyl group-containing fatty acid is more preferable. As such glycerin esters, those that are solid at room temperature and have little bleed from the resin are preferred because they are easy to mix with pigments, especially 12
-Hydroxystearic acid triglyceride is preferred.

The coloring agent of the present invention may be prepared by appropriately mixing a polyhydric alcohol fatty acid ester having a hydroxyl group, which is a pigment dispersant, and a pigment as essential components. The proportion of the polyhydric alcohol fatty acid ester having a hydroxyl group used in preparing the colorant of the present invention varies greatly depending on the type of pigment, but is usually 1 to 250 parts by weight, preferably 5 to 150 parts by weight, based on 100 parts by weight of the pigment. Parts by weight range.

In particular, when using an organic pigment or carbon black, 50 to 100 parts by weight of the pigment is used.
In the case of using an inorganic pigment or an extender pigment other than carbon black, it is particularly preferably in the range of 5 to 50 parts by weight based on 100 parts by weight of the pigment.

The coloring agent of the present invention may be used in any form, such as a so-called dry color in which a pigment is dispersed in a pigment dispersant, or a so-called dry color in which a pigment is dispersed in a pigment dispersion holding medium together with a pigment dispersant. Can be used as a masterbatch color.

The dry color may be produced by uniformly mixing a polyhydric alcohol fatty acid ester having a hydroxyl group, which is a pigment dispersant, and a pigment. The coloring agent obtained in this manner is pulverized and used in the form of a fine powder, if necessary.

[0020] The master batch color may be prepared by dispersing the pigment in a pigment dispersion holding medium together with a pigment dispersant, and the mixing order is not particularly limited. Generally, after the pigment is made into a pigment dispersant, it is further dispersed in a pigment dispersion holding medium at a high concentration. At this time, melt-kneading, pulverization, etc. may be performed as necessary.

As the pigment dispersion holding medium, any known and commonly used medium can be used, such as polyethylene,
Polypropylene, polyethylene terephthalate, polyacetal, ethylene-propylene copolymer, SBR latex, NBR latex, ethylene-vinyl acetate resin, ethylene-acrylic ester resin, styrene-acrylic ester resin, acrylic acid-acrylic ester resin, polyester Resin, polyurethane resin, polyamide resin, phenol resin, furan resin, melamine resin, guanamine resin, epoxy resin, silicone resin,
Examples include fluororesin and polycarbonate. Among these, it is preferable to use polyacetal as an essential component.

[0022] When preparing a masterbatch color, the total weight ratio of the pigment and the pigment dispersant to the pigment dispersion and retention medium is not particularly limited, but it is usually 10% of the pigment dispersion and retention medium.
It is 100 to 200 parts by weight per 0 parts by weight.

The coloring agent of the present invention is preferably used in the form of a dry color because it requires less heat history during coloring. The method for producing colored polyacetal from the colorant of the present invention is not particularly limited, but may be by melt-kneading the polyacetal and the colorant. The conditions for melt-kneading may be such that they are uniformly dispersed, but it is usually carried out within the range of 160 to 200°C.

The coloring agent of the present invention may further contain known and commonly used pigment dispersants such as long-chain aliphatic monocarboxylic acid monoalcohol esters and long-chain aliphatic monocarboxylic acid metal salts.

Examples of such long-chain aliphatic monocarboxylic acid monoalcohol esters include stearyl acetate, isostearyl propionate, eicosyl acetate, myristyl caproate, butyl cyclohexyl propionate, cetyl alcohol acetate, stearyl butyl acetate, and stearyl butyl acetate. Examples of long-chain aliphatic monocarboxylic acid metal salts include calcium stearate, zinc stearate, and aluminum stearate.

[0026] Furthermore, conventionally known additives such as stabilizers and lubricants may be added to the colorant of the present invention, if necessary.

[0027]

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto in any way. In addition, all percentages in the examples are based on weight. Example 1 and Comparative Examples 1 to 7 1.3 parts of a powdered colorant obtained by mixing 100 parts of rutile titanium oxide and 30 parts of the pigment dispersant listed in Table 1 in advance in a small mixer was added to a copolytype. Polyacetal (MFR 9gr/10min,
100 parts of pellets (190° C. x 2.16 kg) were extruded using a twin-screw extruder (L/D=25) at a resin temperature of 190° C. to obtain pellets of a colored acetal composition.

After observing the odor of the obtained pellets, the pellets were made into a film of about 20 μm using a heating melt press at 190° C. and the dispersibility of the pigment was evaluated using a microscope at a magnification of 50 times. Odor evaluation was performed on a three-level scale.

[0029] ○: Odorless or almost no formaldehyde odor. △: A formaldehyde odor is felt. ×: There is a strong odor of formaldehyde. Pigment dispersibility was evaluated on a 5-level scale.

5: Very good - coarse particles (particle size 10
There are no coarse particles (with a particle size of 5 to 1 μm).
There are also almost no medium particles (about 0 μm). 4: Good - There are no coarse particles, but there are some coarse particles.

3: Fair - Some coarse particles were present. 2: Poor - There are coarse particles, and there are many coarse particles. 1: Extremely poor - There are many coarse particles and coarse particles.

Further, the obtained pellets were molded into a flat plate with a thickness of 3 mm using an in-line screw injection molding machine (clamping force 20 t, mold 90° C.) at a resin temperature of 190° C.
The flat plate was exposed to a gear type aging tester heated to 0.degree. C. for 30 minutes, and the weight loss rate (%) relative to the unexposed state was measured.

[0033] The heating weight reduction rate was determined by the following formula.
The smaller the reduction rate, the better the heat resistance.

[0034]

[Math 1]

[0035]

[Table 1]

Example 2 and Comparative Examples 8 to 14 Phthalocyanine blue and various pigment dispersants listed in Table 2 were used in place of titanium oxide and the various dispersants listed in Table 1.
0.4 of the powdered colorant obtained by pre-mixing 0 parts each
A colored polyacetal composition was obtained in the same manner as in Example 1, except that 100% of the composition was added, and then odor, pigment dispersibility evaluation, and heating weight loss rate were measured in the same manner.

The results are shown in Table 2.

[0038]

[Table 2]

Example 3 and Comparative Examples 15 to 21 Carbon black (pH 7.0, furnace) and various pigment dispersants listed in Table 3 were used in place of titanium oxide and the various pigment dispersants listed in Table 1, and 100 parts of each were used. A colored polyacetal composition was obtained in the same manner as in Example 1 except that 0.4 part of the powdered colorant obtained by pre-mixing was added.
Next, odor, pigment dispersibility evaluation, and heating weight loss rate were measured in the same manner.

The results are shown in Table 3.

[0041]

[Table 3]

[0042]

[Effects of the Invention] The coloring agent of the present invention has the particularly remarkable effect of being able to uniformly and finely disperse pigments in polyacetal, and in addition, thermal decomposition of polyacetal is extremely rare.

[0043] Therefore, by coloring with the colorant of the present invention, a polyacetal having excellent heat resistance and appearance can be provided.

Claims (6)

[Claims] 1. A coloring agent for polyacetal comprising a pigment and a pigment dispersant as essential components, characterized in that a polyhydric alcohol fatty acid ester having a hydroxyl group is used as the pigment dispersant. 2. The coloring agent according to claim 1, wherein the pigment dispersant is used in an amount of 5 to 150 parts by weight per 100 parts by weight of the pigment. 3. The coloring agent according to claim 1, wherein the hydroxyl group-containing polyhydric alcohol fatty acid ester is a compound having a structure in which the carboxyl group of the hydroxyl group-containing fatty acid and the hydroxyl group of the polyhydric alcohol are bonded through an ester bond. 4. The coloring agent according to claim 1, wherein the polyhydric alcohol fatty acid ester is a glyceride of hydroxy fatty acid that is solid at room temperature. [Claim 5] Claim 1 wherein the polyhydric alcohol fatty acid ester is hydroxystearic acid triglyceride.
Colorants listed. 6. A method for producing colored polyacetal, which comprises melt-kneading the colorant of claim 1 and polyacetal.