JPH07286074A - Marking composition, molded product, and marking method - Google Patents

Abstract

PURPOSE:To obtain a marking compsn. capable of distinct color development from blackish brown to black in the area thereof irradiated with a laser beam even in a small amt. of a silicon compd. and free of the influence on moldability, polishability, etc., by incorporating a predetermined amt. of the silicon compd. into a polyolefin resin. CONSTITUTION:0.005wt.% to less than 0.5wt.% of a silicon compd., pref. an inorg. silicon compd., further pref. a silicon dioxide compd., is incorporated into a polyolefin resin, pref. PE or PP. Pref. examples of the silicon dioxide compd. include silicon dioxide, mica, kaolin, blast furnace slag, silica sand, diatomaceous earth, and talc, among which mica is most pref. The wt.-average particle size of the silicon compd. is at most 10mum.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a marking composition, a molded product thereof, and a marking method. More specifically, the present invention relates to a polyolefin resin composition for marking that develops a clear black-brown to black color upon irradiation with a laser beam, a molded product thereof, and a laser marking method.

[0002]

2. Description of the Related Art In recent years, electronic parts such as ICs, resistors, capacitors and inductors, electrical parts such as relays, switches, connectors and printed circuit boards, housings for electric products, automobile parts, machine parts, cables, sheets and packaging. As a method for marking the manufacturer name, article name, date of manufacture, etc. on the surface of various containers such as sheets, cards, foods, cosmetics, toiletries or pharmaceuticals, caps of containers, etc. The marking method using laser light (laser marking) has become popular because of its high marking speed, easy automation, and easy process control.

Laser marking is a polymer organic material,
Directly irradiating the surface of parts made of metal, etc. with laser light to change the state of the surface or discolor the colorant in the irradiated area.
Marking is performed by utilizing the change due to bleaching. However, in this marking method, when a polyolefin resin is used as a base material to be marked, the resin sometimes fails to perform marking by transmitting laser light, or the laser light is absorbed to cause etching. Even in such a case, there is a problem in that clear marking cannot be performed only by melting the resin, and it is difficult to develop a clear color even when a coloring agent is used.

In order to solve such a problem, various studies have been made on a color forming agent capable of producing a clear color when applying the laser marking method to a polyolefin resin molded product. For example, in JP-A-60-155493, yellow iron oxide is disclosed in JP-A-61-69488 and JP-A-1-30.
In 6285, the inorganic lead compound is disclosed in JP-A-2-204888.
Then, manganese violet and cobalt violet,
JP-A-63-239059 describes metal compounds such as mercury, cobalt, copper, bismuth and nickel. However, since these compounds are mainly heavy metals,
There are problems such as safety and environmental impact, and in the case of yellow iron oxide, since the compound itself is colored, it cannot be used for resins colored in various hues. It has the problem of being limited. A pearlescent pigment is described in JP-A-60-110737 as a compound which is not colored, but in this case, since it is not colored, it has pearly luster, so it is used for products that do not require pearlescent luster. There is a problem that you cannot do it.

[0005]

Further, since there is no completely colorless coloring agent even if it is not colored, an increase in the amount of addition thereof affects the hue and color tone of the product to be marked. In addition, there is a problem in that the viscosity becomes high and the moldability is affected, and depending on the type of color former, the abrasivity becomes high and the molding machine or kneader is damaged during molding. Therefore, the color former itself is colorless,
There is a demand for a marking composition that develops a clear blackish brown color to a black color with a laser beam even if the amount added is small.

[0006]

The inventors of the present invention have reached the present invention as a result of intensive studies to solve the above-mentioned problems. That is, the present invention provides (1) a polyolefin resin composition for marking, which contains the silicon compound in an amount of 0.005% by weight or more and less than 0.5% by weight based on the polyolefin resin, and (2) the silicon compound is an inorganic silicon compound. (1) The polyolefin resin composition for marking of (1), (3) The polyolefin resin composition for marking of (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 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, and (6) the weight average particle diameter of the inorganic compound is 10
In the polyolefin resin composition for marking of (1) above, which is less than or equal to μ, (7) In the polyolefin resin composition for marking of (1) above, based on the total amount of silicon compounds,
A polyolefin resin composition for marking containing 20 to 1000% by weight of titanium oxide, (8) a resin molded article obtained by molding the polyolefin resin composition for marking of (1) above, and (9) a resin molded article in containers. A certain resin molded product of the above (8), (10) The resin molded product of the above (8), wherein the resin molded product is a film, (11) The above (8) to (1).
A marking method of irradiating the resin molded product of 0) with a laser beam; (12) the marking method of the above (11), wherein the laser beam is an infrared laser beam;
(13) The marking method according to (12), wherein the infrared laser light is far infrared laser light, and (14) the energy of the laser light on the surface of the resin molded product is 2.5 to 20 J.
/ Cm ² above (12) marking method, (1
5) The silicon compound was added to the polyolefin resin in an amount of 0.
A polyolefin for marking, containing 5 to 5% by weight of the masterbatch for resin molding of (8) above, and (16) mica to 0.005% by weight or more and less than 2% by weight with respect to the polyolefin resin. The resin composition, (17) a marking polyolefin resin composition containing 0.005% by weight or more and less than 1% by weight of mica with respect to the polyolefin resin, and (18) the polyolefin resin is polyethylene or polypropylene. 16) or (1
(7) Polyolefin resin composition for marking, (1
9) A resin molded product obtained by molding the polyolefin resin composition for marking according to the above (16) to (18), (20) a resin molded product according to the above (19), wherein the resin molded product is a container,
(21) The resin molded product according to the above (19), wherein the resin molded product is a film, and (22) the molded product characterized by irradiating the resin molded product according to the above (19) to (21) with an infrared laser beam. Marking method, (23) Marking method according to (22) above, wherein the infrared laser light is far infrared laser light, (24) Above, wherein the energy of the infrared laser light on the surface of the resin molded product is 2.5 to 20 J / cm ^2. (22) The marking method.

The marking composition, molded product and marking method of the present invention will be described in detail below. Examples of the polyolefin resin used in the present invention include polyethylene and polypropylene, and have a melting index (MI) of 0.01 to 60, preferably 0.0.
The thing of about 2-55 is good.

The silicon compound used in the present invention acts as a color-developing agent, particularly a color-developing agent that develops from blackish brown to black during laser marking. 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 compounds, mica is most preferable in view of the color density. Examples of the mica include mica belonging to the shirounmo series such as shirounmo, beniunomo, sodownomo, sericite (quinuunmo), vanadinunmo and illite, mica belonging to kurounmo series such as kurounmo, kinkunmo, tetsuunmo, chinwaldunmo, and kairyoku. Natural mica such as stone, celadon stone, muscovite, phlogobite, suzolite, paragonite, vermiculite, and synthetic mica represented by fluorine 4 silicon mica, such as muscovite, phlogobite, szolite, fluorine 4 silicon mica Mica is especially preferred. The silicon dioxide may be in a water-containing state or a non-water-containing state, and examples thereof include crystalline ones, amorphous ones, glass-like ones, colloidal ones, etc. From the viewpoint, amorphous and colloidal ones are preferable. Kaolins have a structure composed of a kaolin-type layer, and include kaolin, kaolinite, nacrite, dikeite, halloysite, hydrohalide, metahalloysite, enderite, anauxite, chrysotile, klonsted stone, antigostone. Part of wright, amesite and chamosite can be mentioned, but kaolin and kaolinite are particularly preferable. Blast furnace slag is a slag that comes out of a steelmaking blast furnace, and is a melt formed by the reaction of impurities in steel with coke ash and limestone, the main components of which are CaO and Si.
O ₂ and Al ₂ O ₃ . Al ₂ O ₃ is 10 to 20%, and most of the rest is CaO and SiO ₂ , but C by weight ratio.
aO: If the SiO ₂ is larger than 1, it is a basic slag, 1
The smaller one is called acidic slag. Both basic slag and acidic slag can be used as a color former. Quartz sand is sand containing quartz grains as a main component, and contains 90% or more of SiO ₂ , and is also a mineral containing feldspar, zircon, magnetite, and the like. Diatomaceous earth is a siliceous deposit composed of the remains of diatoms, which are unicellular algae, and its main component is hydrous amorphous silicon dioxide.
It may be mixed with clay, volcanic ash, organic matter, etc.,
Its color ranges from white to yellowish gray, but white is preferable in order to meet various color tones required for the marking resin. Further, talc is a hydrous silicate mineral of magnesium and has a composition of Mg ₂ Si ₄ O ₁₀ (OH) ₂ . Two or more kinds of these silicon compounds may be used in combination.

The weight average particle diameter of the silicon compound used in the present invention is not particularly limited, but considering the influence on the color tone of the marking resin, it is about 700 μ or less, preferably 10 μ.
Below, it is particularly preferably about 0.5 to 10 μm. The amount used is 0.005 with respect to the polyolefin resin.
% To less than 0.5% by weight, preferably about 0.00
5 or more and less than 0.4% by weight, more preferably about 0.00
The amount is preferably 5% by weight or more and less than 0.3% by weight, particularly preferably about 0.01 to 0.2% by weight. In addition, in mica,
The above range may be used, and 0.005% by weight or more and 2% by weight
Less, preferably about 0.005% or more and less than 1% by weight, more preferably about 0.01 or more and less than 1% by weight,
Particularly preferably, it may be about 0.01 to 0.8% by weight. For kaolins, the above range may be used, but 0.0
It may be 8% by weight or more and less than 0.3% by weight.

In the present invention, when a silicon compound alone is used, a black-brown color is developed, whereas when titanium dioxide is used in combination, the reddish brown color disappears and a gray to black color develops.
This is preferable because the sharpness of the mark is further improved. Titanium dioxide is not particularly limited as long as it is commercially available, but if transparency is not required and black coloring is desired, it is preferable to use commercially available one for pigments. It is preferable to use fine titanium dioxide when a grayish color is desired to be maintained. Titanium dioxide for pigments can be either rutile type or anatase type. The fine-grained titanium dioxide has a particle size of 0.1 μm or less, and is, for example, MT-500B manufactured by Teika Co., Ltd.
Is mentioned. The amount of titanium dioxide used is not particularly limited, but it is preferable to use it in a small amount as much as possible from the viewpoint of cost. Usually, it may be about 1000% by weight or less with respect to the silicon compound. Is about 20 to 1000% by weight. When titanium dioxide for pigments is used, if it is too much, the concealing property of titanium oxide appears and a light color tone is obtained. Therefore, depending on the color tone, the amount used is preferably about 20 to 400% by weight, particularly preferably about 3
It may be preferable to limit the amount to about 0 to 300% by weight.

If necessary, additives and the like can be added to the marking composition of the present invention. As an additive,
For example, colorants, fillers (fillers), lubricants, plasticizers and the like can be mentioned. The colorant that can be used is not particularly limited, but a colorant other than black is preferable, for example, phthalocyanine, azo, disazo, quinacridone, anthraquinone, flavantron, perinone, perylene, dioxazine, condensed azo, various azomethine or methine colorants. Inorganic pigments such as organic dyes, titanium oxide, lead sulfate, zinc oxide, chrome yellow, zinc yellow, chrome vermilion, red iron oxide, cobalt purple, dark blue, chrome green, chromium oxide and cobalt green can be mentioned. These organic and inorganic pigments are in a range that does not affect the sharpness of the colored mark, for example, 0.001 to 3% by weight with respect to the polyolefin resin.
It is added in the range of. Even a black colorant can be used within a range that does not affect the sharpness of the colored mark. Examples of the filler include calcium carbonate, alumina, glass fiber, and other fillers usually used for polyolefin resins. 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.

As the lubricant that can be used, stearic acid, behenic acid and its esters, or salts, waxes such as carnauba wax and polyethylene wax, and various surfactants are used. These are usually added in a proportion of 0.1 to 5.0% by weight with respect to the polyolefin resin, if necessary. Examples of the plasticizer include phthalic acid, phosphoric acid, sebacic acid and other esters. In addition, additives such as antioxidants, heat stabilizers, light stabilizers, and flame retardants that are commonly used in the processing of plastics may be added.
These additives may be used in the form of powder as they are, or may be used in the form of a masterbatch, when producing the polyolefin resin composition for marking of the present invention.

The marking polyolefin resin composition of the present invention comprises a silicon compound, titanium dioxide if desired, and, if necessary, additives such as a colorant, a filler, a lubricant, a plasticizer, and a heat stabilizer to the polyolefin resin. Then, it is obtained by uniformly blending using a kneader such as an extruder, a twin-screw kneader, or a roll mill. Further, the polyolefin resin composition for marking of the present invention is prepared by preparing a masterbatch having a high concentration of a silicon compound or the like, and adding a polyolefin resin and additives such as a filler, if desired, to a uniform blending using a kneader. Can also be obtained by The composition of the present invention thus obtained as it is, or if necessary, further added with an additive such as a polyolefin resin or a filler, is molded into a resin molded product of the present invention by a method known per se. . A masterbatch having a high concentration of a silicon compound or the like is prepared by adding a silicon compound, titanium dioxide if desired, and if necessary, an additive such as a colorant, a filler, a lubricant, a plasticizer or a heat stabilizer to the polyolefin resin. It can be obtained by uniformly blending using a kneading machine such as an extruder, a twin-screw kneader, or a roll mill, and molding into a desired shape such as pellet or marble. The content of the silicon compound in the masterbatch 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 component.

A two-dimensional molded product such as a film is formed by inflation processing, multi-layer inflation processing, T-die film processing, which is used for forming a film of a thermoplastic resin, simultaneous biaxial centrifugal method by a flat film method, or sequential biaxial centrifugal method by vertical and horizontal methods. It is produced by a known method such as a method or a tubular film method. Films produced in this way are used in ordinary thermoplastic resin films such as food packaging, fiber packaging, sundries packaging, packaging of chemicals, tapes, insulating materials, agricultural films, various sheets, various seals, labels, etc. Used in the same field as. Further, the film of the present invention can be laminated by being brought into close contact with various substrates, that is, papers such as kraft paper and high-quality paper, plastic films, metal foils such as aluminum, etc., and thus obtained. Laminate applications include food containers such as milk and alcohol,
Examples include applications such as pharmaceutical packaging materials, food packaging materials, various sheets, various stickers, and labels.

A three-dimensional molded product using the polyolefin resin composition for laser marking of the present invention is injection molded, extruded, blow molded, rotational molded, depending on the molded product.
It is molded by a known method such as foam molding, powder molding or vacuum molding. Specific examples include foods, detergents, pharmaceuticals, cosmetics,
Containers such as beverage products and their caps, food trays, tubes, medical containers, clothing appliances, housings for home appliances, electric appliances, household appliances, automobile parts such as bumpers,
Car interior parts, audio products such as tape cassettes,
Information equipment supplies such as floppy disks, pipes, building materials, industrial parts, various containers, clothing containers, multi-layer containers,
Examples include various sundry goods, various office machines, office supplies and the like, and various molded products containing a thermoplastic resin as a main component, which are generally commercially available.

By irradiating the surface of the thus obtained two-dimensional or three-dimensional molded product with a laser beam, a black-brown to black marking with a sharp contrast can be obtained on the irradiated portion. Examples of the laser light include far-infrared lasers such as carbon dioxide laser (wavelength: about 10600 nm), near-infrared lasers such as YAG laser (wavelength: about 1060 nm), and excimer lasers, but infrared lasers, particularly far-infrared lasers are preferable. The irradiation amount of laser light is, for example, in the case of TEA carbon dioxide gas laser, the energy density of the irradiation source is 0.5 to 1 J / c.
m ² approximately, as the energy density irradiated on the surface of the resin molded product of the present invention, for example 2.5~20J / cm ^2, preferably 2.8~16J / cm ^2, more preferably 3.
It is preferably about 5 to 16 J / cm ² . The energy density (E _d ) of this irradiation portion is higher than that of the irradiation source because the laser beam is condensed and irradiated on the surface of the resin molded product, and is calculated by the following calculation formula. E _d = (total energy amount of irradiation source) / (area of irradiation portion when mask is not used) Since the addition amount of the coloring agent used in the present invention is small, there is an influence on physical properties such as brittleness and processability of resin. rare.

[0018]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, “⊚” means that a black-brown or black mark is obtained and the sharpness thereof is extremely good.
Indicates that a black-brown or black mark was obtained and its sharpness was good, and "x" indicates that the mark was poor in sharpness, or only a white mark was 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 treated for 8 hours, and the glass beads were filtered. Then, the ethyl alcohol was distilled off under reduced pressure and then dried to obtain 99 g of fine mica having an average particle size of 2 μ.

Example 1 Polyethylene (Showlex D500 Sholex S500
3BH MI: 0.3) 1000 parts, mica (made by Kuraray,
Clarite mica (600 W, average particle size 8 μ) 0.5 part was kneaded using a twin-screw kneader at 200 ° C., crushed with a rotoplex mill, and the major axis of 1 mm or less was removed to obtain the marking composition of the present invention. And A film having a thickness of 0.5 mm was formed at 180 ° C. using a 50 ton press, and the surface was marked with a carbon dioxide laser (Zymark 7000 manufactured by Coherent Co., Ltd.) to give a clear black-brown mark (⊚). Obtained.

Example 2 Polyethylene (Showlex D500, Showlex S500)
3BH MI: 0.3) 1000 parts and 5 parts of fine mica of Reference Example 1 were kneaded at 200 ° C. using a twin-screw kneader and crushed by a rotoplex mill, and then those having a major axis of 1 mm or less were removed. The composition was used for marking. A film having a thickness of 0.5 mm was formed at 180 ° C. using a 50 ton press, and the surface was marked with a carbon dioxide laser (Zymark 7000 manufactured by Coherent Co., Ltd.) to give a clear black-brown mark (⊚). Obtained.

Example 3 Polyethylene (Showa Denko Showlex S500
3BH MI: 0.3) 1000 parts, mica (made by Kuraray,
Clarite mica 30C 5 parts average particle size 680μ, titanium dioxide for pigment (Ishihara Sangyo, Taipaque CR-6)
0) 5 parts were kneaded using a twin-screw kneader at 200 ° C., pulverized with 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. Using a 50-ton press, this product was made into a film having a thickness of 0.5 mm at 180 ° C., and the surface was marked with a carbon dioxide laser (Zymark 7000, manufactured by Coherent Co., Ltd.) to give a clear black mark (⊚). Obtained.

Example 4 Polyethylene (UP Polyethylene J110K manufactured by Chisso)
MI: 10) 1000 parts, 1 part of fine mica of Reference Example 1 and 10 parts of fine titanium dioxide (MT-500B manufactured by Teika) were kneaded at 160 ° C. using a biaxial kneader, pulverized with a rotoplex mill, and long diameter 1 mm. The following was removed to provide a marking composition of the present invention. This product was 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 Co., Ltd.) was formed on the surface thereof. ,
Marking was performed using Zymark 7000) to obtain a clear gray-black mark (⊚).

Example 5 Polypropylene (Tonen Polypro J215 M manufactured by Tonen)
I: 15) 1000 parts and 1 part of mica (Kuraray Szolite Mica 325S average particle size 40μ) were kneaded at 220 ° C. using a twin-screw kneader and pulverized with a rotoplex mill to remove particles having a major axis of 1 mm or less. To obtain the marking composition of the present invention. Using an injection molding machine 2
It was molded into a plate at 20 ° C., and its surface was marked with a carbon dioxide laser (Zymark 7000, manufactured by Coherent Co., Ltd.) to obtain a clear black-brown mark (◯).

Example 6 Polypropylene (Chisso Polypro K-81 manufactured by Chisso)
40T MI: 40) 1000 parts and kaolin (average particle size 2μ) 2 parts were kneaded at 220 ° C. using a biaxial kneader,
After crushing 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 into a plate shape at 220 ° C. using an injection molding machine, and the surface thereof was marked with a carbon dioxide laser (Zymark 7000 manufactured by Coherent Co., Ltd.) to obtain a blackish brown mark (◯).

Example 7 Polypropylene (Asahi Kasei Polypro E100 manufactured by Asahi Kasei)
MI: 0.5) 1000 parts and artificial mica (MK-100 made by Corp Chemical Co., Ltd., average particle size 2.5 μ) 5 parts were kneaded at 220 ° C. using a twin-screw kneader and pulverized with a rotoplex mill, and then the major axis was 1 mm or less. Were removed to obtain the marking composition of the present invention. Using a 50-ton press, this product was made into a film having a thickness of 0.5 mm at 200 ° C., and a carbon black laser (Zymark 7000, manufactured by Coherent Co., Ltd.) was used to mark the surface to give a clear black-brown mark (⊚). Obtained.

Example 8 Polyethylene (UP Polyethylene J110K manufactured by Chisso)
MI: 10) 1000 parts, mica (Kuraray, Clarite mica 600W, average particle size 8μ) 0.3 parts, titanium dioxide (Ishihara Sangyo Taipek R-820) 0.3 parts using a biaxial kneader 160 After kneading at 0 ° C. and 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 product was molded into a plate shape at 150 ° C. using an injection molding machine, and a carbon dioxide laser (Zymark 7000, manufactured by Coherent Co., Ltd.) was formed on the surface of the plate.
Marking is done using a clear gray black mark (◎)
Got

Example 9 Polyethylene (Showlex D500 Sholex S500
3BH MI: 0.3) 1000 parts and blast furnace slag (average particle size 8μ) 1 part were kneaded at 200 ° C. using a twin-screw kneader, crushed with a rotoplex mill, and those with a major axis of 1 mm or less were removed. The marking composition of the invention was obtained. 0.5mm at 180 ℃ using a 50 ton press
The surface of the film was marked with a carbon dioxide laser (Zymark 7000, manufactured by Coherent Co., Ltd.) to obtain a clear black-brown mark (◯).

Example 10 Polyethylene (Showlex D500 Sholex S500
3BH MI: 0.3) 1000 parts and silica sand powder (average particle size 10μ) 1 part were kneaded at 200 ° C. using a twin-screw kneader, crushed with a rotoplex mill, and those with a major axis of 1 mm or less were removed. The marking composition of the invention was obtained. 0.5mm at 180 ℃ using a 50 ton press
The surface of the film was marked with a carbon dioxide laser (Zymark 7000, manufactured by Coherent Co., Ltd.) to obtain a clear black-brown mark (⊚).

Example 11 Polyethylene (Showa Denko Showlex S500
3BH MI: 0.3) 1000 parts and diatomaceous earth (average particle size 6 μ) 1 part were kneaded at 200 ° C. using a biaxial kneader,
After crushing 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 made into a film of 0.5 mm at 180 ° C. using a 50 ton press, and its surface was marked with a carbon dioxide laser (Zymark 7000 manufactured by Coherent Co., Ltd.) to obtain a clear black-brown mark (⊚). .

Example 12 Polyethylene (UP Polyethylene J110K manufactured by Chisso)
MI: 10) 1000 parts, blast furnace slag (average particle size 8μ)
3 parts, fine titanium dioxide (Taika MT-500B)
Ten parts were kneaded using a biaxial kneader at 160 ° C., pulverized with 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 product was molded on a plate at 150 ° C. using an injection molding machine, and a carbon dioxide laser (Zymark 7 manufactured by Coherent Co., Ltd.) was formed on the surface of the plate.
000) to give a clear black mark (⊚).

Example 13 Polyethylene (manufactured by Chisso UP Polyethylene J110K)
MI: 10) 1000 parts and 1 part of talc (average particle size 2μ) are kneaded at 160 ° C. using a twin-screw kneader, crushed by a rotoplex mill, and those having a major axis of 1 mm or less are removed for marking according to the present invention. It was a composition. This product was molded into a plate at 150 ° C. using an injection molding machine, and a carbon dioxide gas laser (Zymark 700 manufactured by Coherent Co., Ltd.)
0) was used to obtain a clear black-brown mark (⊚).

Comparative Example 1 Polyethylene (Showrex S500 manufactured by Showa Denko)
3BH MI: 0.3) 1000 parts, mica (made by Kuraray,
Clarite mica 600W, average particle size 8μ) 50 parts was kneaded at 200 ° C. using a twin-screw kneader, crushed with a rotoplex mill, and then, those having a major axis of 1 mm or less were removed to obtain a marking composition for comparison. . This was made into a film having a thickness of 0.5 mm at 180 ° C. using a 50 ton press, and a carbon dioxide laser (manufactured by Coherent Co., Ltd.
When making a mark using Zymark 7000),
Only white marks (x) were obtained.

Comparative Example 2 Polyethylene (Showlex D500 Sholex S500
3BH MI: 0.3) 18 using a 50 ton press
A film with a thickness of 0.5 mm at 0 ° C. is formed, and a carbon dioxide laser (Zymark 700 manufactured by Coherent Co., Ltd.) is formed on the surface thereof.
When marking was performed using (0), no mark was obtained (x).

Comparative Example 3 Polyethylene (Showa Denko Showlex S500
3BT MI: 0.3) 1000 parts and talc (average particle size 2μ) 50 parts were kneaded at 200 ° C. using a twin-screw kneader and pulverized with a rotoplex mill, then those with a major axis of 1 mm or less were removed for comparison. Marking composition. 0.5mm at 180 ℃ using a 50 ton press
When the surface of the film was marked with a carbon dioxide gas laser (Zymark 7000, manufactured by Coherent Co., Ltd.), only white marks (x) were obtained.

Experimental Example Polyethylene (Showlex D500, Showlex S500
3BH) and a predetermined amount of color former are added and kneaded, and a carbon dioxide laser (manufactured by Laser Technics Co., Ltd., Blazer 6000 output 26.1 kv total energy 3.8 J) with a predetermined focusing ratio on the surface of a plate-shaped test piece. Then, the marking was performed by irradiating with, and the relationship between the energy density of the laser irradiation portion and the sharpness of the mark was examined. The results are shown in Table 1. In the table, "○" indicates that a clear black-brown mark was obtained, "△" indicates that a distinguishable black-brown mark was obtained, and "x" indicates that the mark cannot be distinguished. There is.

[0037]

[Table 1] Table 1 No. Coloring agent addition amount Energy density (J / cm ² ) (%) of irradiated area 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 × △ ○

[0038]

EFFECTS OF THE INVENTION According to the present invention, the laser light-irradiated portion of the polyolefin resin develops from blackish brown to black even with an extremely small addition amount of less than 0.5% by weight with respect to the polyolefin resin. A black-brown to black mark can be formed by laser on the surface of a molded product of a polyolefin resin without affecting the color tone and without affecting the physical properties of the resin composition such as moldability and polishing properties.

Claims (24)

[Claims] 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 claim 1, wherein the silicon compound is an inorganic silicon compound. 3. The polyolefin resin composition for marking according to claim 2, wherein the inorganic silicon compound is a silicon dioxide compound. 4. The polyolefin resin composition for marking according to claim 3, wherein the silicon dioxide compound is silicon dioxide, mica, kaolin, blast furnace slag, silica sand, diatomaceous earth or talc. 5. The polyolefin resin composition for marking according to claim 1, wherein the polyolefin resin is polyethylene or polypropylene. 6. The polyolefin resin composition for marking according to claim 1, wherein the weight average particle diameter of the silicon compound is 10 μm or less. 7. The marking polyolefin resin composition according to claim 1, wherein the total amount of silicon compounds is 20 to 1
A polyolefin resin composition for marking containing 000% by weight of titanium oxide. 8. A resin molded product obtained by molding the polyolefin resin composition for marking according to claim 1. 9. The resin molded product according to claim 8, which is a container. 10. The resin molded product is a film or the like.
Resin molded product. 11. A marking method for a molded article, which comprises irradiating the resin molded article according to claim 8 with a laser beam. 12. The marking method according to claim 11, wherein the laser light is infrared laser light. 13. The marking method according to claim 12, wherein the infrared laser light is far infrared laser light. 14. The energy of laser light on the surface of the resin molded product is 2.5 to 20 J / cm ^2.
Marking method. 15. 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. 16. A marking polyolefin resin composition 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 0.005% by weight or more and less than 1% by weight of mica with respect to the polyolefin resin. 18. The marking polyolefin resin composition according to claim 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 claim 16 or 18. 20. The resin molded product according to claim 19, which is a container. 21. The resin molded product is a film or the like.
9 resin molded product. 22. A marking method for a molded article, which comprises irradiating the resin molded article according to claim 19 with an infrared laser beam. 23. The marking method according to claim 22, wherein the infrared laser light is far infrared laser light. 24. The marking method according to claim 22, wherein the energy of infrared laser light on the surface of the resin molded product is 2.5 to 20 J / cm ² .