JP2004027238A - Marking composition, molded product, and marking method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a marking composition which comprises such a coloring agent as is colorless in itself and which produces even in a slight addition amount a color from vivid blackish brown to black by means of a laser beam. <P>SOLUTION: The marking polyolefin resin composition contains a silicon compound of from more than 0.005 % by weight to less than 0.5 % by weight relative to a polyolefin resin. The coloring agent, even in an extremely slight addition amount of less than 0.5 % by weight to the polyolefin resin, can produce a color from blackish brown to black on a part irradiated by a laser beam , so that the coloring agent can give a mark having a color from blackish brown to black on the surface of a molded product of the polyolefin resin, without influencing the color hue and color tone of the product to be subjected to a marking and also without influencing the physical properties such as a moldability and a polishability. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a marking composition, a molded product thereof, and a marking method. More specifically, the present invention relates to a marking polyolefin resin composition which develops a clear blackish brown to black color upon irradiation with a laser beam, a molded product thereof, and a laser marking method.

In recent years, electronic components such as ICs, resistors, capacitors, and inductors, electrical components such as relays, switches, connectors, and printed circuit boards, housings for electrical products, automotive components, mechanical components, cables, sheets, packaging sheets, cards, and foods Non-contact and fast marking speed as a method for marking the name of manufacturer, article name, date of manufacture, etc. on the surface of various containers such as cosmetics, toiletry articles or pharmaceuticals, caps of containers, etc. A marking method using a laser beam (laser marking) is widely used because automation and process control are easy.

Laser marking is performed by directly irradiating the surface of a component made of a high molecular weight organic material, metal, etc. with laser light, and using the change in the surface state or the change due to discoloration or decolorization of the colorant in the irradiated part. Is what you do. However, in this marking method, when a polyolefin resin is used as a substrate to be marked, depending on the case, the resin transmits laser light and cannot be marked, or laser light is absorbed and etching occurs. Even in this case, there is a problem that clear marking cannot be performed only by melting the resin, and that even if a coloring agent is used, it is difficult to form a clear color.

In order to solve such a problem, in applying a laser marking method to a polyolefin resin molded product, various studies have been made on a color former that clearly produces a color. For example, in Patent Literature 1, yellow iron oxide, in Patent Literature 2, Patent Literature 3, an inorganic lead compound, in Patent Literature 4, manganese violet and cobalt violet, and in Patent Literature 5, mercury, cobalt, copper, bismuth, nickel, etc. Metal compounds are each described. However, since these compounds are mainly heavy metals, there are problems such as safety and impact on the environment, and in the case of yellow iron oxide, since the compounds themselves are colored, they are colored in various hues. There is a problem that the range of use is limited, for example, it cannot be used as a resin. Patent Literature 6 describes a pearlescent pigment as a compound that is not colored, but in this case, it is not colored but has a pearly luster, so that it cannot be used for products that do not require pearlescent luster. There are points.
JP-A-60-155493 JP-A-61-69488 JP-A-1-306285 JP-A-2-204888 JP-A-63-239059 JP-A-60-110737

In addition, since there is no completely colorless coloring agent even if it is not colored, there is a problem that if the addition amount is large, the hue and color tone of the product to be marked are affected, and the viscosity is low. However, there is also a problem that the moldability is increased and the formability is affected, and depending on the type of the coloring agent, the abrasion property is increased and the molding machine or the kneading machine is damaged during molding. Accordingly, there is a need for a marking composition which is colorless in color forming agent itself, and which develops a clear black-brown color to black color with a laser beam even when the amount of the coloring agent is very small.

The present inventors have intensively studied to solve the above-mentioned problems, and as a result, have arrived at the present invention. That is, the present invention
(1) a polyolefin resin composition for marking containing a silicon compound in an amount of 0.005% by weight or more and less than 0.5% by weight based on the polyolefin resin;
(2) The polyolefin resin composition for marking according to the above (1), wherein the silicon compound is an inorganic silicon compound;
(3) The polyolefin resin composition for marking according to the above (2), wherein the inorganic silicon compound is a silicon dioxide compound.
(4) The polyolefin resin composition for marking according to (3) above, wherein the silicon dioxide-based compound is silicon dioxide, mica, kaolin, blast furnace slag, silica sand, diatomaceous earth, or talc.
(5) The polyolefin resin composition for marking according to the above (1), wherein the polyolefin resin is polyethylene or polypropylene;
(6) The polyolefin resin composition for marking according to (1), wherein the weight average particle diameter of the inorganic compound is 10 μm or less,
(7) The polyolefin resin composition for marking according to (1), wherein the polyolefin resin composition for marking contains 20 to 1000% by weight of titanium oxide based on the total amount of the silicon compound;
(8) A resin molded product obtained by molding the polyolefin resin composition for marking of (1) above,
(9) The resin molded product according to the above (8), wherein the resin molded product is containers.
(10) The resin molded product according to the above (8), wherein the resin molded product is a film.
(11) A method for marking a molded article, which comprises irradiating the resin molded article according to (8) to (10) with a laser beam;
(12) The marking method according to the above (11), wherein the laser light is an infrared laser light,
(13) The marking method according to the above (12), wherein the infrared laser light is far infrared laser light,
(14) The marking method according to (12) above, wherein the energy of the laser beam on the surface of the resin molded product is 2.5 to 20 J / cm2.
(15) The master batch for a resin molded product according to the above (8), containing the silicon compound in an amount of 0.5 to 5% by weight based on the polyolefin resin;
(16) a polyolefin resin composition for marking containing mica in an amount of 0.005% by weight or more and less than 2% by weight based on the polyolefin resin;
(17) a polyolefin resin composition for marking containing mica in an amount of 0.005% by weight or more and less than 1% by weight based on the polyolefin resin;
(18) The polyolefin resin composition for marking according to the above (16) or (17), wherein the polyolefin resin is polyethylene or polypropylene;
(19) A resin molded product obtained by molding the polyolefin resin composition for marking according to any one of (16) to (18),
(20) The resin molded product according to the above (19), wherein the resin molded product is containers.
(21) The resin molded article according to the above (19), wherein the resin molded article is a film.
(22) A method for marking a molded article, which comprises irradiating the resin molded article according to (19) to (21) with an infrared laser beam.
(23) The marking method according to the above (22), wherein the infrared laser light is a far infrared laser light,
(24) The marking method according to the above (22), wherein the energy of the infrared laser beam on the surface of the resin molded product is 2.5 to 20 J / cm2;
About.

According to the present invention, even a very small addition amount of less than 0.5% by weight with respect to the polyolefin resin causes the laser light-irradiated portion of the polyolefin resin to develop a color from blackish brown to black, which affects the hue and color tone of the product to be marked. A black-brown to black mark can be formed on the surface of a molded product of a polyolefin resin by a laser without affecting the physical properties such as moldability and abrasiveness of the resin composition.

<< Polyolefin resins used in the present invention include polyethylene, polypropylene and the like, and those having a melting index (MI) of about 0.01 to 60, preferably about 0.02 to 55 are good.

珪 素 The silicon compound used in the present invention acts as a color former during laser marking, particularly as a color former that develops a blackish brown to black color. As the silicon compound, an inorganic silicon compound, particularly a silicon dioxide compound such as silicon dioxide, mica, kaolin, blast furnace slag, silica sand, diatomaceous earth, and talc is preferable. Among the silicon dioxide-based compounds, mica is most preferred in view of the color density. Examples of the mica include, for example, mica belonging to the chrysomorpha series, such as the Japanese brown moth, black-tailed moth, thorium moth, sericite (Kinuumumo), vanadinmo, illite, etc .; Natural mica such as stone, celadonite, muscovite, phlogovite, suzolite, paragonite, vermiculite, and synthetic mica represented by tetrasilicic mica, such as muscovite, phlogovite, suzolite, and tetrasilicic mica Mica is particularly preferred. The silicon dioxide may be in a hydrated state or in a non-hydrated state, and examples thereof include crystalline, amorphous, glassy, and colloidal ones. From the viewpoint, amorphous and colloidal materials are preferred. Kaolins have a structure composed of a kaolin-type layer, and include kaolin, kaolinite, nacrite, deckite, halloysite, hydrohaloysite, metahaloysite, enderite, anauxite, chrysotile, clonsteadite, and antigoite. Some of wright, amethyst, and chamosite are mentioned, and kaolin and kaolinite are particularly preferred. Blast-furnace slag is slag from a smelting furnace for steelmaking, and is a melt formed by the reaction of impurities in iron and steel with coke ash and limestone, and its main components are CaO, SiO2, and Al2 O3. Al2 O3 is 10 to 20% and most of the rest is CaO and SiO2, but those with a weight ratio of CaO: SiO2 larger than 1 are called basic slag and those smaller than 1 are called acidic slag. Both basic slag and acidic slag can be used as coloring agents. Silica sand is a sand containing quartz grains as a main component, and is a mineral containing 90% or more of SiO2 and feldspar, zircon, magnetite and the like. Diatomaceous earth is a siliceous sediment composed of the remains of a diatom, a unicellular algae, and its main component is hydrous amorphous silicon dioxide. Clay, volcanic ash, organic matter, and the like may be mixed, and the color ranges from white to yellow-gray, but white is preferable in order to correspond to various color tones required for the resin for marking. Talc is a hydrated silicate mineral of magnesium and has a composition of Mg2 Si4 O10 (OH) 2. Two or more of these silicon compounds may be used in combination.

The weight average particle size of the silicon compound used in the present invention is not particularly limited, but considering the effect on the color tone of the marking resin, about 700 μm or less, preferably 10 μm or less, particularly preferably about 0.5 to 10 μm. It is. The amount used is 0.005% by weight or more and less than 0.5% by weight, preferably about 0.005% or more and less than 0.4% by weight, more preferably about 0.005% by weight or more, based on the polyolefin resin. And less than 0.3% by weight, particularly preferably about 0.01 to 0.2% by weight. In the case of mica, the content may be in the above range, and may be from 0.005% by weight to less than 2% by weight, preferably from about 0.005% by weight to less than 1% by weight, more preferably from about 0.01 to 1% by weight. %, Particularly preferably about 0.01 to 0.8% by weight. In the case of kaolins, the content may be in the above range, but may be not less than 0.08% by weight and less than 0.3% by weight.

In the present invention, the use of only a silicon compound causes blackish brown coloration, whereas the use of titanium dioxide eliminates the reddish color of blackish brown, develops a gray to black color, and improves the sharpness of the mark, which is preferable. . Titanium dioxide is not particularly limited as long as it is generally commercially available, but when a black color is not required without requiring transparency, it is preferable to use a commercially available product for pigments. When a grayish color is desired to be maintained, fine titanium dioxide is preferably used. Titanium dioxide for pigments can be either rutile or anatase. The fine titanium dioxide has a particle size of 0.1 μm or less, and for example, MT-500B manufactured by Teica Corporation. The use amount of titanium dioxide is not particularly limited, but is preferably used as small as possible from the viewpoint of cost. Usually, it may be about 1000% by weight or less based on the silicon compound. However, when using fine titanium dioxide, the use amount is preferably Is about 20 to 1000% by weight. In the case of using titanium dioxide for a pigment, if it is too much, the concealing property of the titanium oxide appears and the color becomes light, so the amount of use is preferably about 20 to 400% by weight, particularly preferably about 30 to 300% by weight depending on the color. In some cases, it is preferable to limit the amount to about% by weight.

添加 Additives and the like can be added to the marking composition of the present invention as needed. Examples of the additives include a colorant, a filler (fillers), a lubricant, and a plasticizer. The colorant that can be used is not particularly limited, but a non-black colorant is preferable, for example, phthalocyanine, azo, disazo, quinacridone, anthraquinone, flavanthrone, perinone, perylene, dioxazine, condensed azo, azomethine or methine-based various colorants. Inorganic pigments such as organic dyes, titanium oxide, lead sulfate, zinc oxide, chrome yellow, zinc yellow, chrome vermillion, red iron, cobalt purple, navy blue, chrome green, chromium oxide, and cobalt green. These organic and inorganic pigments are added in a range that does not affect the sharpness of the formed mark, for example, in a range of 0.001 to 3% by weight based on the polyolefin resin. Note that even a black colorant can be used in a range that does not affect the sharpness of the formed mark. Examples of the filler include fillers usually used for polyolefin resins, such as calcium carbonate, alumina, and glass fiber. These are added in a range that does not affect the sharpness of the colored mark, for example, in a range of 0.001 to 3% by weight based on the polyolefin resin. Examples of usable lubricants include stearic acid, behenic acid and esters or salts thereof, waxes such as carnauba wax and polyethylene wax, and various surfactants. These are added, if necessary, usually in a ratio of 0.1 to 5.0% by weight based on the polyolefin resin. Examples of the plasticizer include esters such as phthalic acid, phosphoric acid, and sebacic acid. In addition, additives commonly used in processing plastics, such as antioxidants, heat stabilizers, light stabilizers, and flame retardants, may be added. These additives may be used as a powder or in the form of a master batch when preparing the polyolefin resin composition for marking of the present invention.

The polyolefin resin composition for marking of the present invention is obtained by adding a silicon compound, optionally titanium dioxide, and further, if necessary, additives such as a coloring agent, a filler, a lubricant, a plasticizer, and a heat stabilizer to the polyolefin resin. It is obtained by blending uniformly using a kneader such as a ruder, a twin-screw kneader or a roll mill. In addition, the polyolefin resin composition for marking of the present invention is to produce a master batch having a high concentration of a silicon compound or the like, and to add a polyolefin resin and, if desired, an additive such as a filler, and uniformly blend the mixture using a kneader. Can also be obtained by The composition of the present invention thus obtained is added as it is, or if necessary, further to an additive such as a polyolefin resin or a filler, and molded into a resin molded product of the present invention by a method known per se. . In addition, a master batch having a high concentration of a silicon compound or the like is obtained by adding a silicon compound, optionally titanium dioxide, and further, if necessary, additives such as a coloring agent, a filler, a lubricant, a plasticizer, and a heat stabilizer to the polyolefin resin. It is obtained by uniformly mixing using a kneader such as an extruder, a twin-screw kneader, or a roll mill, and molding into a desired shape such as a pellet or a marble. The content of the silicon compound in the master batch is about 0.5 to 5% by weight, preferably about 0.5 to 2% by weight, based on the polyolefin resin.

Examples of the resin molded product include a two-dimensional molded product such as a film and a three-dimensional molded product such as a container, a cap and a part.

For two-dimensional molded products such as films, inflation processing, multilayer inflation processing, T-die film processing, vertical and horizontal simultaneous biaxial centrifugal method using a flat film method, or vertical and horizontal sequential biaxial centrifugal method used for forming a thermoplastic resin into a film, tubular, It is produced by a known method such as a film method. Films produced in this way are used for ordinary thermoplastic resin films such as food packaging, textile packaging, miscellaneous goods packaging, pharmaceutical packaging, tapes, insulating materials, agricultural films, various sheets, various seals, labels, etc. Used in the same fields as Further, the film of the present invention can be laminated with various substrates, that is, papers such as kraft paper and woodfree paper, plastic films, metal foils such as aluminum and the like, and thus obtained. Examples of the use of the laminate include food containers for milk and alcohol, packaging materials for pharmaceuticals, food packaging materials, various sheets, various seals, labels, and the like.

The three-dimensional molded product using the polyolefin resin composition for laser marking of the present invention may be formed by a known method such as injection molding, extrusion molding, hollow molding, rotational molding, foam molding, powder molding, vacuum molding, etc., depending on the molded product. Molded. Specific examples include containers for foods, detergents, pharmaceuticals, cosmetics, beverage products, and their caps, food trays, tubes, medical containers, clothing, housing for home appliances, electric appliances, household goods, bumpers, and other vehicles. Parts, automotive interior goods, audio equipment such as tape cassettes, information equipment supplies such as flexible disks, pipes, building materials, industrial parts, various containers, clothing containers, multilayer containers, daily miscellaneous goods, various office machines, office work Examples of such articles include various molded products mainly containing a thermoplastic resin which is generally commercially available, such as articles.

By irradiating the surface of the two-dimensional or three-dimensional molded article thus obtained with laser light, a black-brown to black marking with a clear contrast is obtained on the irradiated part. Examples of the laser light include a far-infrared laser such as a carbon dioxide laser (wavelength of about 10600 nm), a near-infrared laser such as a YAG laser (wavelength of about 1060 nm), and an excimer laser. An infrared laser, particularly a far-infrared laser is preferable. The irradiation amount of the laser beam is, for example, about 0.5 to 1 J / cm @ 2 in the case of a TEA carbon dioxide laser, and the energy density of the irradiation on the surface of the resin molded product of the present invention is, for example, 2.5. -20 J / cm2, preferably 2.8-16 J / cm2, more preferably 3.5-16 J / cm2. The energy density (Ed) of the irradiated portion is higher than that of the irradiation source because the laser beam is condensed and radiated to the surface of the resin molded product, and can be obtained by the following formula.
Ed = (total energy amount of irradiation source) / (area of irradiation part when mask is not used)
In the present invention, since the amount of the coloring agent to be used is small, there is almost no influence on physical properties such as brittleness and workability of the resin.

Next, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. In the examples, ◎ indicates that a black-brown or black mark was obtained and its sharpness was extremely good, ○ indicates that a black-brown or black mark was obtained and its sharpness was good, and `` x '' indicates that This indicates that the definition of the mark is poor or that only a white mark can be obtained.

Reference Example 1
100 ml of glass beads (1 mmφ), 100 g of mica (Kuraray, Clarite Mica 600 W, average particle size 8 μ), and 186 g of ethyl alcohol were added to a 500 ml ceramic sand mill, and the mixture was treated for 8 hours, and the glass beads were filtered off. After distilling off under reduced pressure, the residue was dried to obtain 99 g of fine mica having an average particle size of 2 μm.

Example 1
1000 parts of polyethylene (Showrex S5003BH MI: 0.3, manufactured by Showa Denko) and 0.5 parts of mica (Kuraray, Kuralite mica 600W, average particle size 8μ) are kneaded at 200 ° C using a biaxial kneader, and the funnel is added. After pulverizing with a plex mill, those having a major axis of 1 mm or less were removed to obtain a marking composition of the present invention. This was made into a 0.5 mm thick film at 180 ° C. using a 50-ton press, and its surface was marked using a carbon dioxide laser (Zymark 7000, manufactured by Coherent) to give a clear black-brown mark (◎). Obtained.

Example 2
1000 parts of polyethylene (Showrex S5003BH MI: 0.3 manufactured by Showa Denko) and 5 parts of the fine mica of Reference Example 1 are kneaded at 200 ° C. using a biaxial kneader, pulverized by a rotoplex mill, and having a major axis of 1 mm or less. Was removed to obtain a marking composition of the present invention. This was made into a 0.5 mm thick film at 180 ° C. using a 50-ton press, and its surface was marked using a carbon dioxide laser (Zymark 7000, manufactured by Coherent) to give a clear black-brown mark (◎). Obtained.

Example 3
1000 parts of polyethylene (Showrex S5003BH MI: 0.3 manufactured by Showa Denko), 5 parts of mica (manufactured by Kuraray, Clarite Mica 30C average particle size: 680μ), titanium dioxide for pigment (manufactured by Ishihara Sangyo, Taipaque CR-60) 5 The part was kneaded at 200 ° C. using a biaxial kneader, pulverized by a rotoplex mill, and those having a major axis of 1 mm or less were removed to obtain a marking composition of the present invention. This was made into a film having a thickness of 0.5 mm at 180 ° C. using a 50-ton press, and the surface thereof was marked using a carbon dioxide gas laser (manufactured by Coherent Corporation, Zymark 7000) to give a clear black mark (◎). Obtained.

Example 4
1000 parts of polyethylene (UP Polyethylene J110K MI: 10 manufactured by Chisso), 1 part of fine mica of Reference Example 1, and 10 parts of fine titanium dioxide (MT-500B manufactured by Teica) are kneaded at 160 ° C. using a biaxial kneader, and then rotoplex. After pulverizing with a mill, those having a major axis of 1 mm or less were removed to obtain a marking composition of the present invention. This is molded into a plate at 150 ° C. using an injection molding machine (SAV-40 manufactured by Yamashiro Seiki, hereinafter referred to as an injection molding machine), and a carbon dioxide laser (manufactured by Coherent Corporation) is formed on the surface thereof. , Zymark 7000) to obtain a clear gray-black mark (◎).

Example 5
1000 parts of polypropylene (Tonen Polypro J215 MI: 15 manufactured by Tonen) and 1 part of mica (Szolite Mica 325S manufactured by Kuraray, average particle size: 40 μm) are kneaded at 220 ° C. using a biaxial kneader, and pulverized by a rotoplex mill. Those having a size of 1 mm or less were removed to obtain a marking composition of the present invention. This was molded into a plate at 220 ° C. using an injection molding machine, and its surface was marked using a carbon dioxide gas laser (manufactured by Coherent, Zymark 7000) to obtain a clear black-brown mark (マ ー ク).

Example 6
1000 parts of polypropylene (Nisso polypro K-8140T MI: 40 manufactured by Chisso) and 2 parts of kaolin (average particle size: 2μ) are kneaded at 220 ° C using a biaxial kneader, crushed by a rotoplex mill, and having a long diameter of 1 mm or less. Was removed to obtain a marking composition of the present invention. This was molded into a plate at 220 ° C. using an injection molding machine, and its surface was marked using a carbon dioxide gas laser (manufactured by Coherent, Zymark 7000) to obtain a black-brown mark (○).

Example 7
1000 parts of polypropylene (Asahi Kasei Polypro E100 MI: 0.5) and 5 parts of artificial mica (MK-100, average particle size: 2.5 μm, manufactured by Corp Chemical) are kneaded at 220 ° C. using a biaxial kneader, and then a rotoplex mill. After pulverization, a material having a major axis of 1 mm or less was removed to obtain a marking composition of the present invention. This was made into a 0.5 mm thick film at 200 ° C. using a 50-ton press, and its surface was marked using a carbon dioxide gas laser (manufactured by Coherent Corporation, Zymark 7000) to give a clear black-brown mark (◎). Obtained.

Example 8
1000 parts of polyethylene (UP Polyethylene J110K MI: 10, manufactured by Chisso), 0.3 parts of mica (Kuraray, 600 W of Clarite Mica, average particle size 8μ), 0.3 parts of titanium dioxide (Taipe R-820, manufactured by Ishihara Sangyo) The mixture was kneaded at 160 ° C. using a biaxial kneader, pulverized by a rotoplex mill, and then, those having a major axis of 1 mm or less were removed to obtain a marking composition of the present invention. This was molded into a plate at 150 ° C. using an injection molding machine, and its surface was marked using a carbon dioxide gas laser (manufactured by Coherent, Zymark 7000) to obtain a clear gray-black mark (マ ー ク). .

Example 9
1000 parts of polyethylene (Shorex S5003BH MI: 0.3, manufactured by Showa Denko) and 1 part of blast furnace slag (average particle size: 8μ) are kneaded at 200 ° C using a biaxial kneader, pulverized by a rotoplex mill, and a long diameter of 1 mm or less. Was removed to obtain a marking composition of the present invention. This was made into a 0.5 mm film at 180 ° C. using a 50-ton press, and the surface thereof was marked using a carbon dioxide laser (Zimark 7000, manufactured by Coherent) to obtain a clear black-brown mark (（). .

Example 10
1000 parts of polyethylene (Showa Denko Shorex S5003BH MI: 0.3) and 1 part of silica sand powder (average particle size: 10 μm) are kneaded at 200 ° C. using a biaxial kneader, pulverized by a rotoplex mill, and a long diameter of 1 mm or less. Was removed to obtain a marking composition of the present invention. This was made into a 0.5 mm film at 180 ° C. using a 50-ton press, and its surface was marked using a carbon dioxide gas laser (manufactured by Coherent, Zymark 7000) to obtain a clear black-brown mark (◎). .

Example 11
1000 parts of polyethylene (Showrex S5003BH MI: 0.3 manufactured by Showa Denko) and 1 part of diatomaceous earth (average particle size: 6 μm) are kneaded at 200 ° C. using a biaxial kneader, pulverized by a rotoplex mill, and mixed with a long diameter of 1 mm or less. Those were removed to obtain a marking composition of the present invention. This was made into a 0.5 mm film at 180 ° C. using a 50-ton press, and its surface was marked using a carbon dioxide gas laser (manufactured by Coherent, Zymark 7000) to obtain a clear black-brown mark (◎). .

Example 12
1000 parts of polyethylene (UP Polyethylene J110K MI: 10 manufactured by Chisso), 3 parts of blast furnace slag (average particle size: 8 μ), and 10 parts of fine titanium dioxide (MT-500B manufactured by Teica) are kneaded at 160 ° C. using a biaxial kneader. After pulverizing with a rotoplex mill, those having a major axis of 1 mm or less were removed to obtain a marking composition of the present invention. This was molded on a plate at 150 ° C. using an injection molding machine, and its surface was marked using a carbon dioxide laser (Zimark 7000, manufactured by Coherent) to obtain a clear black mark (◎).

Example 13
1000 parts of polyethylene (UP Polyethylene J110K MI: 10 manufactured by Chisso) and 1 part of talc (average particle size: 2μ) are kneaded at 160 ° C using a biaxial kneader, pulverized by a rotoplex mill, and those having a major diameter of 1 mm or less are removed. Thus, a marking composition of the present invention was obtained. This was molded into a plate at 150 ° C. using an injection molding machine, and its surface was marked using a carbon dioxide gas laser (manufactured by Coherent, Zimark 7000) to obtain a clear black-brown mark (◎).

Comparative Example 1
1000 parts of polyethylene (Showrex S5003BH MI: 0.3, manufactured by Showa Denko) and 50 parts of mica (Kuraray, Clarite Mica 600W, average particle size: 8μ) are kneaded at 200 ° C using a biaxial kneader, and a rotoplex mill. After pulverization, a material having a major axis of 1 mm or less was removed to obtain a marking composition for comparison. This was made into a 0.5 mm thick film at 180 ° C. using a 50 ton press, and the surface was marked using a carbon dioxide laser (Coherent, Zymark 7000). Could not be obtained.

Comparative Example 2
Polyethylene (Showa Denko Shorex S5003BH MI: 0.3) was formed into a 0.5 mm thick film at 180 ° C. using a 50-ton press, and the surface thereof was coated with a carbon dioxide gas laser (Coherent, Zymark 7000). When the marking was applied, no mark was obtained (x).

Comparative Example 3
1000 parts of polyethylene (Showrex S5003BT MI: 0.3 manufactured by Showa Denko) and 50 parts of talc (average particle size: 2μ) are kneaded at 200 ° C. using a biaxial kneader, pulverized by a rotoplex mill, and then mixed with a long diameter of 1 mm or less. Those were removed to obtain a marking composition for comparison. This was made into a 0.5 mm film at 180 ° C. using a 50-ton press, and the surface thereof was marked with a carbon dioxide laser (Zimark 7000, manufactured by Coherent Inc.). As a result, only a white mark (×) was obtained. Did not.

Experimental Example A predetermined amount of a coloring agent was added to polyethylene (Showa Denko Shorex S5003BH) and kneaded, and a carbon dioxide gas laser (manufactured by Laser Technics Co., Ltd., Blazer 6000 output) was formed on the surface of a plate-shaped test piece at a predetermined light-collecting magnification. Marking was performed by irradiating 26.1 kv of the total energy of 3.8 J), and the relationship between the energy density of the laser beam irradiated portion and the sharpness of the mark was examined. Table 1 shows the results. In the table, “○” indicates that a clear black-brown mark was obtained, “△” indicates that a recognizable black-brown mark was obtained, and “×” indicates that the mark could not be discriminated. I have.

(Table 1)
Table 1
No. Coloring agent addition amount Energy density of irradiated part (J / cm2)
(%) 2.2 2.9 4.1 6.5 8.6
1. Mica 0.1 × △ ○
0.3 × ○
2. Kaolin 0.1 × △ ○
0.3 × △ ○
3. Blast furnace slag 0.1 × △ ○
0.3 × △ ○
4. Talc 0.1 × △ ○
0.3 × △ ○
5. Silicon dioxide 0.1 × △ ○
0.3 × △ ○

Claims (15)

A polyolefin resin composition for marking containing a silicon compound in an amount of 0.005% by weight or more and less than 0.5% by weight based on the polyolefin resin. The polyolefin resin composition for marking according to claim 1, wherein the silicon compound is an inorganic silicon compound. The polyolefin resin composition for marking according to claim 2, wherein the inorganic silicon compound is a silicon dioxide compound. The polyolefin resin composition for marking according to claim 3, wherein the silicon dioxide-based compound is silicon dioxide, kaolins, blast furnace slag, silica sand, diatomaceous earth or talc. The polyolefin resin composition for marking according to claim 1, wherein the polyolefin resin is polyethylene or polypropylene. The polyolefin resin composition for marking according to claim 1, wherein the weight average particle diameter of the silicon compound is 10 µ or less. The polyolefin resin composition for marking according to claim 1, comprising 20 to 1000% by weight of titanium oxide based on the total amount of the silicon compound. A resin molded product obtained by molding the polyolefin resin composition for marking according to claim 1. The resin molded product according to claim 8, wherein the resin molded product is a container. The resin molded product according to claim 8, wherein the resin molded product is a film. A method for marking a molded article, comprising irradiating the resin molded article according to any one of claims 8 to 10 with a laser beam. The marking method according to claim 11, wherein the laser beam is an infrared laser beam. 13. The marking method according to claim 12, wherein the infrared laser light is a far infrared laser light. The method according to claim 11, wherein the energy of the laser beam on the surface of the resin molded product is 2.5 to 20 J / cm2. The masterbatch for a resin molded product according to claim 8, wherein the silicon compound is contained in an amount of 0.5 to 5% by weight based on the polyolefin resin.