KR100496947B1 - Laser marking polyoxymethylene resin composition - Google Patents

Abstract

The present invention relates to a polyoxymethylene resin composition for laser marking, and more particularly, to a particle size of 10-50 nm, DBP (dibutyl Phthalate) oil absorption 40-100 with respect to 100 parts by weight of polyoxymethylene (polyoxymethylene) It relates to a polyoxymethylene resin composition for laser marking comprising 0.01 to 3.0 parts by weight of carbon-bone black coated with -OH group and 0.01 to 5.0 parts by weight of a dihydrazide compound, which is ㏄ / 100 mg. According to the present invention, by using a dihydrazide compound as a thermal stability improver to improve the thermal stability of the molded article for laser marking, and substantially minimize the release of formaldehyde during processing, has excellent laser marking properties compared to the existing products, Provided is a polyoxymethylene resin composition for laser marking that can improve frictional wear resistance, durability, chemical resistance, fatigue resistance, and the like. In addition, by laser marking using a Nd: YAG laser or the like on a molded article formed using the polyoxymethylene resin composition for laser marking according to the present invention, it is possible to display the shape of white or many colors on various color products, It is possible to freely change the design through the connection with the CAD has the advantage of obtaining a laser marking molded product that can respond to a wide range of quality requirements.

Description

Laser marking polyoxymethylene resin composition

The present invention relates to a polyoxymethylene resin composition for laser marking, and more particularly, by using a dihydrazide compound as a heat stability enhancer to improve the thermal stability of the laser marking molded article, and to release the formaldehyde during processing It relates to a polyoxymethylene resin composition for laser marking that can be substantially minimized.

As a method of marking desired letters, symbols, and the like on the surface of a resin molded article or a molded article coated with resin, a printing method using a thermosetting ink has been generally performed. However, in the case of polyacetal, when such a printing method is applied, since the polyacetal is a crystalline resin, there are few inks with satisfactory adhesiveness, and it is impossible to perform printing with substantially high adhesion without pretreatment. In addition, depending on the use environment, there is a problem that the scratch resistance, abrasion resistance and chemical resistance of the printing portion by the ink are not sufficient.

Accordingly, a method of marking a thermoplastic resin by irradiating laser light has been proposed as a marking method capable of solving the problem of the printing method using the thermosetting ink.

The laser marking method can be quickly applied when applied to small changes and small parts, and does not require pretreatment and post-treatment, and it does not require additional materials and additional processes, thereby simplifying the process. have. In addition, it is possible to freely change the design through the linkage with the auto cad has the advantage of relatively low equipment investment cost, but there is a disadvantage that is inadequate compared to the printing method when applied to a large area and multicolor.

On the other hand, one of the laser technologies used in the laser marking method is Nd: YAG (neodymium: yttrium aluminum garnet) laser marking technology. The type of laser marking using the Nd: YAG laser can be divided into metal, plastic, silicon, wood, paper, leather and glass according to the marking material, and secondly, is the material cut or the surface marked? Can be classified according to the method. Finally, depending on the way of marking the surface, it is embossed and engraved, and the groove of the processing surface is carved to be engraved, the method of discoloring the surface of the material to be marked, and the surface to be processed are inflated for the marking effect. It can be divided largely by the method of obtaining.

In addition, such marking may include engraving mainly used for night design of the electric switch and plastic marking in such a manner that the portion where the laser is scanned is evaporated to remove burrs without causing burrs; Stamping and fading useful for marking most metals and plastics except copper, aluminum, etc. in such a way that a few burrs remain on the marking surface to which the beam is scanned and the color changes simultaneously with the marking on the scanning surface; It is a method of changing the color only by causing instant chemical change without imprinting marking surface, and there are discoloration and bleaching, which is a method of discoloration marking of plastic surface such as keyboard or metal surface using high frequency value. .

For example, Japanese Patent Laid-Open No. 58-67496 introduces a relatively simple method of imparting a desired marking by using a physical change of the laser processing surface, that is, a thermal processing method, and Japanese Patent Laid-Open No. 63-216790, In Japanese Patent Application Laid-Open No. 61-41320 and Japanese Patent Laid-Open No. Hei 1-306285, a method of expressing laser marking property by adding a filler capable of discoloration and discoloration is introduced.

On the other hand, many of the methods using such a discolorable and discolorable filler are characterized by clearly giving a marking of a color different from that of the base material on a base material colored with a pigment or the like. In particular, research has been actively conducted on the composition for laser marking to obtain a clear white marking on a black substrate.

For example, Japanese Patent Laid-Open No. 11-140271 discloses a resin composition for laser marking comprising polyoxymethylene and carbon black having a particle size of 17 to 90 nm and a DBP oil absorption of 70 to 200 ml / 100 mg. Is disclosed. In the case of using the resin composition for marking according to the patent, there is an advantage in that it is possible to give a bright and clear white laser marking to a colored substrate, especially a black substrate, but thermal stability is improved by using carbon black and pigment. There is a disadvantage that it may be poor, leading to discoloration and deterioration of mechanical properties during subsequent use of the molded article.

On the other hand, U.S. Patent No. 5,218,041 discloses polyoxymethylene, endocopolymer, phenolic antioxidant and carbon black as a composition for solving the above-mentioned problems and reducing the amount of formaldehyde released when processing the mixture at high temperature. Including polyoxymethylene molding materials is introduced. However, according to the patent, although the amount of formaldehyde emission can be reduced, there is a disadvantage in that the mechanical properties of the polyoxymethylene resin is reduced by the influence of the incopolymer.

Accordingly, in the present invention, extensive research has been conducted to solve the problems described above. As a result, a thermally stable molded article for laser marking is used by using a dihydrazide compound as a thermal stability enhancer in the resin polyoxymethylene composition for laser marking. It has been found that it is possible to improve the stability and very substantially minimize the release of formaldehyde during processing, and the present invention has been completed based on this.

Accordingly, an object of the present invention is to provide a polyoxymethylene resin composition for laser marking having excellent thermal stability.

Another object of the present invention is to provide a polyoxymethylene resin composition for laser marking in which the emission of formaldehyde is substantially minimized during processing.

Still another object of the present invention is to provide a polyoxymethylene resin composition for laser marking that exhibits good color and vivid brightness.

The resin composition for laser marking according to the present invention for achieving the above and other objects includes 0.01 to 3.0 parts by weight of carbon black, and 0.01 to 5.0 parts by weight of the dihydrazide compound, based on 100 parts by weight of polyoxymethylene.

Hereinafter, the present invention will be described in more detail.

As described above, in the present invention, by using a dihydrazide compound as a thermal stability enhancer, the thermal stability of the laser marking molded article can be improved, and the laser marking polyoxy which can substantially minimize the emission of formaldehyde during processing. Methylene resin composition is provided.

Laser marking composition according to the present invention is carbon coated with -OH group, the particle size is 10-50nm, DBP (dibutyl Phthalate) oil absorption 40-100㏄ / 100mg with respect to 100 parts by weight of polyoxymethylene (polyoxymethylene) 0.01-3.0 parts by weight of black and 0.01-5.0 parts by weight of a dihydrazide compound.

The polyoxymethylene resin used in the present invention is a homopolymer composed of oxymethylene units represented by the following general formula (1), or a copolymer in which units of the general formula (1) and units of the following general formula (2) are randomly bonded.

-(-CH ₂ O-)-

-[-(CX ₁ X ₂ ) _x O-]-

Wherein X ₁ and X ₂ are the same as or different from each other, hydrogen, an alkyl group or an aryl group, x is an integer from 2 to 6, provided that neither X ₁ nor X ₂ is hydrogen. The average molecular weight of the polyoxymethylene resin of the present invention is preferably 10,000 to 200,000.

The oxymethylene homopolymer may be prepared by polymerizing formaldehyde or a cyclic oligomer thereof, that is, trioxane, and the oxymethylene copolymer in which the unit of Formula 1 and the unit of Formula 2 are combined with formaldehyde or a cyclic oligomer thereof It can be obtained by random copolymerization of the cyclic ether compound represented by the formula (3) or the cyclic formal compound represented by the following formula (4).

Wherein X ₃ , X ₄ , X ₅ and X ₆ are the same or different from each other hydrogen or an alkyl group and may be bonded to the same carbon atom or to another carbon atom, n and m each being an integer of 2 to 6 to be.

In the copolymerization monomer used in the random copolymerization, cyclic ether compounds include ethylene oxide, propylene oxide, butylene oxide and phenylene oxide, and the like, and cyclic formal compounds include 1,3-dioxolane and diethylene glycol. Formal, 1,3-propanediol formal, 1,4-butanediol formal, 1,3-dioxepan formal and 1,3,6-trioxocane and the like. Preferably, at least one monomer selected from monomers consisting of ethylene oxide, 1,3-dioxolane, 1,4-butanediol formal, and the like is preferably used. The monomer may be added to trioxane or formaldehyde, which is the main monomer, in the presence of a Lewis acid catalyst, and randomly copolymerized to obtain an oxymethylene copolymer having a melting point of 150 ° C. or more and two or more bonding carbon atoms in the main chain.

In the oxymethylene copolymer, the molar ratio of the oxymethylene bond structure to the oxymethylene repeating unit is 0.05 to 50, preferably 0.1 to 20.

Polymerization catalysts used for the polymerization of the oxymethylene polymer include BF ₃ · OH _2, BF ₃ · OEt ₂ , BF ₃ · OBu _2, BF ₃ · CH ₃ CO ₂ H, BF ₃ · PF ₅ · HF, BF _{3-10-hydroxy-acetamide} may be made of phenol and the like, in which Et denotes an ethyl group, and, Bu means butyl group. Preferably, BF ₃ · OEt ₂ and BF ₃ · OBu ₂ are used. The addition amount of the polymerization catalyst is preferably in the range of 2 × 10 ⁻⁶ to 2 × 10 ⁻² moles with respect to 1 mole of trioxane.

The polymerization may be carried out in the form of bulk polymerization, suspension polymerization or solution polymerization, the reaction temperature is 0 to 100 ℃, preferably 20 to 80 ℃.

On the other hand, as a deactivator for deactivating the remaining catalyst after polymerization, tertiary amines such as triethylamine, cyclic sulfur compounds such as thiophene, phosphorus compounds such as triphenylphosphine, and alkyl-substituted meramine compounds These are all Lewis base materials having unshared electron pairs and form complex salts with the catalyst.

In the polymerization reaction of polyoxymethylene, an alkyl substituted phenol or an ether may be used as a chain transferring agent, and it is particularly preferable to use an alkyl ether such as dimethoxymethane.

Among the polyoxymethylene resins prepared as described above, the most preferred compounds of the present invention are homopolymers or copolymers of polyoxymethylene having a melting point of about 160 ° C. or more, a crystallinity of 65 to 85%, and an average molecular weight of 10,000 to 200,000.

According to the present invention, carbon black is used as a material that selectively absorbs laser light in order to obtain clear marking with lower laser energy. In general, colorability by carbon black on substrates formed from polyoxymethylene resins, in particular laser marking on blackish black and carbon black blended resins in black coloration, average particle size and dibutyl phthalate (DBP) oil absorption of That is, it largely depends on the particle size which is the size of carbon black particle alone, the structure which is the size which particle | grain aggregated, and the compounding quantity of carbon black. On the other hand, since the coloring properties, in particular, the blackness and laser marking properties tend to be opposed by the amount of carbon black added, it is important to select a suitable carbon black so that good colorability and excellent laser marking properties can be obtained at the same time. Preferably, the carbon black used in the present invention preferably has a particle size of 10 to 50 nm and a DBP oil absorption of 40 to 100 cc / 100 mg. Here, when the particle size of the carbon black is less than 10 nm, the dispersibility in the resin deteriorates, and when it exceeds 50 nm, the colorability of the polyoxymethylene resin deteriorates. Moreover, when DBP oil absorption amount of the said carbon black is less than 40 cc / 100 mg, the coloring property of a polyoxymethylene resin worsens, and when it exceeds 100 cc / 100 mg, dispersibility in resin will worsen. In particular, the carbon black coated with -OH group is improved in dispersibility due to compatibility with the end group of polyoxymethylene resin, in order to obtain a satisfactory ebon blackness to obtain even a small amount of carbon black desirable.

In the present invention, the carbon black is blended into the marking composition to provide good white marking on the surface of the black or dark substrate, as well as to color the gray substrate using a small amount of carbon black, or to color other complex colors. It can also be applied to use. In this case, the amount of the carbon black used is preferably 0.01 to 3.0 parts by weight with respect to 100 parts by weight of polyoxymethylene, and satisfactory luster may not be obtained when the amount is less than 0.01 parts by weight, and when it exceeds 3.0 parts by weight, the marking property is poor. Become.

According to the present invention, in addition to the carbon black, titanium dioxide (TiO ₂ ), an inorganic pigment, an organic pigment, and the like, which are additives capable of improving laser marking property, may be further selectively used as a material for absorbing laser light.

On the other hand, when the above-described carbon black and other pigments and the like are used, the polyoxymethylene molding material prepared therefrom may cause deposition of molds or deterioration of mold release properties, or decolorization and mechanical properties during subsequent use of molded articles. There is a problem with unsatisfactory thermal stability leading to degradation. In addition, there is a disadvantage that can result in unpleasant odor due to the release of formaldehyde during processing at high temperatures.

Thus, in the present invention, it is possible to express better color invariance and permanent brightness of the color, as well as to provide a dehydra as a thermal stability enhancer to provide a polyoxymethylene molding material having excellent thermal stability during processing and at high temperatures. Zide compounds are used.

The dehydrazide compound is a compound containing reactive hydrogen, which generally generates an addition reaction with an inorganic acid or an organic acid, or generates a polymer reactant through a condensation reaction of a derivative by reaction with a reactive compound, that is, an organic group or a radical. It is used as an epoxy resin hardener, a crosslinking agent for acrylic esters, an improving agent for synthetic fibers or synthetic resins, a fiber treating agent or a radical removing agent.

In the present invention, the thermal reduction of the polyoxymethylene resin composition for laser marking by removing decomposition-causing substances that may be caused by the addition of carbon black and other pigments using the strong reducing reaction-inducing property of the dihydrazide compound. It is possible to improve the stability and minimize the release of formaldehyde during processing at high temperatures. Preferably, the dihydrazide compound is oxalic dihydrazide, malonic dihydrazide, succinic dihydrazide, adipic dihydrazide, sebacic dihydrazide, dodecanoic One of dihydrazide, isophthalic dihydrazide, piperazine N, N'-dihydrazide, m-benzene-dihydrazide, and p-benzene-dihydrazide can be selected.

In this case, the amount of the dihydrazide compound is 0.01 to 5.0 parts by weight based on 100 parts by weight of polyoxymethylene is good, if the amount is less than 0.01 parts by weight of the thermal stability improvement effect is less, if the amount exceeds 5.0 parts by weight of poly by side reaction It causes thermal stability and deterioration of physical properties of the oxymethylene resin composition.

On the other hand, in the present invention, as described above, in order to give good brightness and bright white laser marking property, titanium dioxide can be selectively used further. At this time, the amount of the titanium dioxide used is preferably less than 5.0 parts by weight based on 100 parts by weight of the total laser marking resin composition.

In addition, an inorganic pigment for expressing the specific color may optionally be further used in order not only to the black substrate surface but also to realize good white marking on the surface of the substrate colored with a specific color other than black. Preferably, the inorganic pigments include cobalt green, cobalt blue, chrome oxide green, cadmium pigments, nickel / chrome titanates and One or more of the ultramarine blues may be selected. In this case, the amount of the inorganic pigment may be less than 10 parts by weight based on 100 parts by weight of the total laser marking polyoxymethylene resin composition.

In addition, an organic pigment for expressing the specific color may be selectively used to obtain a marking of a specific color other than a white color on the surface of the substrate colored with the specific color. Preferably, the organic pigment may be selected from one or more of anthra quinoids, phthalocyanine blue, phthalocyanine green, and chromophtal red. At this time, the amount of the organic pigment is preferably less than 10 parts by weight based on 100 parts by weight of the total laser marking polyoxymethylene resin composition.

In the present invention, in addition to the above-mentioned components, additives or fillers known in the art may be further used, if necessary, within the range of not degrading the marking property by laser irradiation. For example, various stabilizers, antioxidants, lubricants, plasticizers, nucleating agents, mold release agents, antistatic agents and surfactants for improving weather resistance and the like can be further used.

On the other hand, clear marking can be easily performed only by irradiating a laser beam to the specific position of the molded article formed from the resin composition mentioned above. At this time, in order to perform marking of a desired shape, for example, a method of scanning the surface of the object with a spot of a suitable size, and a surface of the object using a laser beam of a desired shape by masking the laser light. The method to irradiate is mentioned.

Although it does not specifically limit as a kind of laser used, For example, a carbon dioxide laser, a ruby laser, a semiconductor laser, an argon laser, an excimer laser, a YAG laser etc. are mentioned. Especially, Nd; YAG laser is preferable. As the oscillation form, both continuous oscillation and pulse oscillation can be used. Preferably, a scanning type Nd; YAG laser, which is pulsed at high speed using a Q switch with continuous oscillation, is preferable.

As described above, the thermal stability of the molded article is improved by using the resin composition for laser marking according to the present invention, the release of formaldehyde is very substantially minimized during processing, and is often generated in the molded article to which the conventional printing method is applied. Durability problems due to peeling can be solved, and aging problems due to deterioration of chemical resistance during oil or solvent immersion can also be solved. In addition, it has excellent laser marking properties as compared to the existing products, the basic properties as acetal (acetal), that is, mechanical properties, chemical resistance and fatigue resistance is sufficiently maintained, and can be applied to parts requiring frictional wear resistance.

In addition, laser marking using Nd: YAG laser or the like on a molded article formed using the polyoxymethylene resin composition for laser marking described above is faster than conventional printing methods, and does not require pretreatment and post-treatment, and is linked with autocad. It is possible to change the design freely through the advantage that you can obtain a molded product that can respond to a wide range of quality requirements. In addition, there is an advantage that can display a bar code, numbers, letters, pictures and two-dimensional symbols of white or multiple colors on a variety of color products except white molded products.

Therefore, the resin composition for laser marking according to the present invention is a field in which the printed molded article is immersed in various oils or solvents; Parts requiring display of a plurality of colors of barcodes, numbers, letters, designs, and two-dimensional symbols; A part in which peeling phenomenon occurs at a printing part of a printed molded article; And it can be widely applied to parts that require excellent frictional wear characteristics and laser marking properties. For example, the present invention may be applied to keyboard keytop parts, mobile phone keypad parts, automotive interior / exterior parts, automotive fuel gauge parts, buckles, zippers, souvenirs, toy parts, and the like.

In one embodiment of the present invention, the polyoxymethylene resin, carbon black, and titanium dioxide were melt-kneaded using a twin screw extruder, and the melt from the extruder die was cooled through a cooling bath and prepared in pellet form. The injection molded product was prepared using the polyoxymethylene composition thus prepared using an injection machine.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples.

Examples 1-5 and Comparative Examples 1-2

* Physical properties of the compositions shown in the following Examples and Comparative Examples were measured as follows:

(1) melt index (MI); Formability (fluidity)

According to the ASTM D1238 method, the weight of the sample extruded from an orifice having a constant internal diameter for 10 minutes at a temperature of 190 ° C. and a load of 2.16 kg was measured. Higher value means better moldability (fluidity) and lower value means poor moldability (fluidity).

(2) tensile strength and tensile elongation

Tensile strength and elongation were measured according to ASTM D638 method. Higher values indicate better tensile strength and elongation, and lower values indicate poor tensile strength and elongation.

(3) Izod impact strength

Izod impact strength (Notched) was measured according to the ASTM D256 method. Higher values mean better Izod impact strength and lower values mean poor Izod impact strength.

(4) Formaldehyde gas generation amount

50 mL of distilled water was placed in a 1L polyethylene bottle, and the test piece was placed so as not to come into contact with distilled water. After standing for 3 hours at 60 ° C UL-Spec Oven, acetyl acetone and ammonium acetate were added to distilled water to form a chromophore. The concentration of formaldehyde gas dissolved in distilled water was measured using a spectrometer. Higher value means higher formaldehyde generation and lower value means lower formaldehyde generation.

(5) weight loss rate

The degree to which the mass of the sample decreases after 1 hour of stay at 222 ° C. in a nitrogen atmosphere at TGA (Thermogravity Analysis) was measured. Higher values mean lower thermal stability and lower values mean higher thermal stability.

(6) laser marking (L-ratio)

A 'KEPITAL' logo was marked on a 10 X 20 mm square using an Nd: YAG 1064 nm laser. L-ratio was measured at 10 ° viewing angle with D65 light source using SP-88 spectrophotometer of X-Rite, which is L-white / L-black ratio. The higher this value, the better.

Example 1

1.0 parts by weight of oxalic dihydrazide (hereinafter referred to as OADH) with respect to 100 parts by weight of polyoxymethylene copolymer resin (trade name: KEPITAL F20-01 manufactured by Korea Engineering Plastics Co., MI = 9.5 g / 10 minutes, hereinafter referred to as POM), 0.15 parts by weight of carbon black coated with —OH group and 0.05 parts by weight of titanium dioxide were melt kneaded using a twin screw extruder, and the melt from the extruder die was cooled through a cooling bath and prepared in pellet form. After preparing a test piece using the polyoxymethylene composition obtained from the injection machine, and then measured the physical properties according to the above-described measuring method, the results are shown in Tables 1 and 2.

Example 2

Except for further adding 0.5 parts by weight of inorganic pigment (Ultramarine Blue) was carried out in the same manner as in Example 1 to prepare a test piece, after measuring the physical properties according to the above-described measuring method, the results are shown in Table 2 Shown in

Example 3

Except for further adding 0.5 parts by weight of organic pigment (Phthalocyanine Blue) to prepare a test piece in the same manner as in Example 1, after measuring the physical properties according to the above-described measuring method, the results are shown in Table 2 Shown in

Example 4

Except not using titanium dioxide, the test piece was prepared in the same manner as in Example 1, and then the physical properties were measured according to the above-described measuring method, and the results are shown in Table 2 below.

Comparative Examples 1 to 3

A test piece was prepared in the same manner as in Example 1 except that the content of carbon black was changed as shown in Table 2 without using oxalic dihydrazide, and then physical After measuring the properties, the results are shown in Table 2 below.

Item Test Method (ASTM) Exam conditions unit Example 1 Physical properties importance D792 23 ℃ - 1.41 Water absorption D570 23 ℃ 60% RH % 0.22 Thermal properties MI D1238 190 ℃ g / 10min 9.8 Melting point DSC method - ℃ 165 Mechanical property The tensile strength D638 23 ± 2 ℃ kgf / ㎠ 600 Tensile elongation 50 ± 5% RH % 60 Flexural strength D790 23 ± 2 ℃ kgf / ㎠ 860 Flexural modulus 50 ± 5% RH kgf / ㎠ 25,000 Izod impact strength (notched) D256 Notchedt = 3.2mm kgfcm / cm 7.0 Mold Shrinkage (t5mm, Φ100mm) Flow direction - % 2.0

Sample POM (part by weight) Carbon black (part by weight) Thermal stabilizer (parts by weight) Color additive (part by weight) L-B Formaldehyde Gas Generation (ppm) Laser marking color Background color Example 1 100 0.15 OADH 1.0 Titanium Dioxide 0.05 2.5 3.4 White black Example 2 100 0.20 OADH 1.0 Titanium Dioxide 0.05, Ultramarine Blue 0.5 - 3.9 White Ultramarine Blue Example 3 100 0.20 OADH 1.0 Phthalocyanine Blue 0.5 - 4.3 blue Ultramarine Blue Example 4 100 0.15 OADH 1.0 - 2.0 3.6 White black Comparative Example 1 100 0.15 - Titanium Dioxide 0.05 2.4 9.0 White black Comparative Example 2 100 0.4 OADH 1.0 - 0.52 4.7 grey black Comparative Example 3 100 0.4 - - 0.47 11.3 grey black

As described above, by using the dihydrazide compound as a thermal stability enhancer in the polyoxymethylene resin composition for laser marking according to the present invention, the enthusiasm stability of the molded article is improved and the release of formaldehyde during processing is substantially minimized. Compared with the product, it is possible to obtain a laser marking molded product having excellent laser marking properties and improved friction wear resistance, durability, chemical resistance and fatigue resistance. In addition, by laser marking the molded article formed using the resin composition for laser marking according to the present invention using an Nd: YAG laser or the like, it is possible not only to display the shape of white or multiple colors on various color products, but also to existing printing methods. Compared to this, it is faster and requires no pretreatment or post-treatment, and it is possible to freely change the design through linkage with auto CAD, so that a molded product for laser marking can meet a wide range of quality requirements.

Claims (8)

0.01 to 3.0 parts by weight of carbon black coated with —OH group, having a particle size of 10-50 nm and a DBP (dibutyl Phthalate) oil absorption of 40-100 dl / 100 mg, based on 100 parts by weight of polyoxymethylene, and A polyoxymethylene resin composition for laser marking, comprising 0.01 to 5.0 parts by weight of a dihydrazide compound. delete The method of claim 1, wherein the dihydrazide compound is oxalic dihydrazide, malonic dihydrazide, succinic dihydrazide, adipic dihydrazide, sebacic dihydrazide, dodecano Ic dihydrazide, isophthalic dihydrazide, piperazine N, N'-dihydrazide, m-benzene-dihydrazide, and p-benzene-dihydrazide A composition, characterized in that. The composition according to any one of claims 1 to 3, wherein the resin composition for laser marking further comprises TiO ₂ . The resin composition for laser marking according to any one of claims 1 to 3, wherein the resin composition for laser marking is cobalt green, cobalt blue, chromium oxide green, cadmium pigments, At least one inorganic pigment selected from the group consisting of nickel / chrome titanates and ultramarine blue. The resin composition of claim 4, wherein the resin composition for laser marking is cobalt green, cobalt blue, chromium oxide green, cadmium pigments, nickel / chromium titanate, and the like. at least one inorganic pigment selected from the group consisting of chrome titanates and ultramarine blue. The resin composition according to any one of claims 1 to 3, wherein the resin composition for laser marking is anthra quinoids, phthalocyanine blue, phthalocyanine green, and chromophtal red. At least one organic pigment selected from the group consisting of a) characterized in that it further comprises. The resin composition of claim 4, wherein the resin composition for laser marking is at least one selected from the group consisting of anthra quinoids, phthalocyanine blue, phthalocyanine green, and chromophtal red. The composition further comprises an organic pigment of.