JPH0885757A - Polyamide resin composition excellent in laser markability - Google Patents

Abstract

PURPOSE: To obtain a polyamide resin composition excellent in laser markability and capable of being furnished with a mark with high contrast by using a polyamide resin containing a suitable amount of water. CONSTITUTION: This resin omposition comprises 100 pts.wt. polyamide resin having a water content of 0.06-12wt.% and 0.001-5 pts.wt. carbon. Examples of the polyamide resins used include a ring-opening polymer of a lactam, a polycondensate of an aminocarboxylic acid and a polycondensate of a dibasic acid with a diamine. Nylon 46, nylon 6 and nylon 66 are particularly desirable. The water content is adjusted so that it has a suitable value before or after molding. It is desirable that the carbon is the one having high thermal conductivity. Desirable examples of processes for mixing the components include the one comprising homogenizing them by mixing a part or all of them at one time or separately with a mixer and the one comprising uniformly dispersing them by previously dry-blending them and melt-kneading the dry blend with a heated extruder.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyamide resin composition which can be marked with a laser beam.

[0002]

2. Description of the Related Art In the past, printing with ink has been mainly used as a marking method on the surface of a resin molded product. However, when the printed portion is made of plastics, the ink adhesion should be improved. It is necessary to remove the release agent and the like compounded at the time of molding, and for this reason, fluorocarbon cleaning of plastics has been performed. However, the CFC cleaning treatment is not preferable from the viewpoint of preventing ozone layer depletion. Therefore, the development of innovative means is desired. However, a technology capable of omitting the fluorocarbon cleaning step must simultaneously reduce the printing cost, and technically, it must be able to meet the needs for fine line fine printing. And
Recently, a marking method using a laser beam has been attracting attention because printing can be performed easily and efficiently.

The two types of laser marking devices currently in use are a carbon dioxide gas laser and a YAG laser. In order to effectively carry out laser marking, it is necessary to modify the plastic in advance so that it is easily exposed to light. This is a technique in which a filler that absorbs light and heat is mixed in the material in advance so that marking can be performed by foaming, decomposition, or the like during laser irradiation. For example, JP-A-57-116620 discloses that laser marking can be performed by adding carbon black and / or graphite to a thermoplastic resin. Further, Japanese Patent Application Laid-Open No. 1-254743 discloses that titanium oxide or a mixture thereof with carbon black is added to a means for improving the marking property of a thermoplastic resin by a YAG laser. However, when carbon black is used, it is unavoidable that the whiteness of the surface of the molded product at the laser light irradiation portion is lowered, and further improvement has been demanded.

As a result of diligent studies, the present inventor has found that by performing laser marking on a polyamide resin containing an appropriate amount of water, it is possible to maintain a high whiteness of a portion irradiated with a laser beam and to exhibit a clear contrast. The invention was reached.

[0005]

An object of the present invention is to provide a polyamide resin composition excellent in laser marking. Another object of the present invention is to provide a material which can make clear marking with a clear contrast by means of laser light. Further objects and advantages of the present invention will be apparent from the following description.

[0006]

According to the present invention, the above objects and advantages are
This is achieved by a polyamide resin composition containing a sufficient amount of water for improving the laser marking property of the polyamide resin and further containing a specific amount of carbon.

The polyamide resin used in the present invention is not particularly limited.

Examples of the polyamide resin used in the present invention include ring-opening polymerization products of cyclic lactams, polycondensation products of aminocarboxylic acids, polycondensation products of dibasic acids and diamines, and specifically nylons. 6, nylon 6
6, nylon 46, nylon 610, nylon 612,
Aliphatic polyamides such as nylon 11 and nylon 12,
Poly (meta-xylene adipamide), poly (hexamethylene terephthalamide), poly (hexamethylene isophthalamide), poly (tetramethylene isophthalamide)
And aliphatic-aromatic polyamides, and copolymers and mixtures thereof. Of these, nylon 46 and nylon 6 are preferable. In addition, nylon 66
Is also preferable.

As the nylon 46 resin, adipic acid or a functional derivative thereof is used as an acid component, and tetramethylenediamine or a functional derivative thereof is used as an amine component. A polyamide obtained by a condensation reaction is mainly used. A part of the acid component or the tetramethylenediamine component may be replaced with another copolymer component.

Preferred embodiments of nylon 46 resin are JP-A-56-149430 and JP-A-56-14943.
No. 1 publication.

The nylon 46 resin used in the present invention is
It is desirable that the intrinsic viscosity measured with m-cresol at 35 ° C. is in the range of 0.80 to 1.90, and more preferably 0.90 to 1.50. When nylon 46 having an intrinsic viscosity of more than 1.90 is used, the fluidity at the time of molding is poor, the gloss of the appearance of the obtained molded product is lost, and the mechanical properties and thermal properties vary. It is not preferable because it becomes large. On the other hand, if the intrinsic viscosity is lower than 0.80, the mechanical strength of the molded product will be reduced.

Carbon, which is one of the components of the present invention, includes
Those having high thermal conductivity are preferable. These are characterized by having a relatively bulky structure such as a crystal structure in which graphitization has progressed or a secondary structure that forms a chain-like aggregate.

When carbon is added, if the amount of carbon is less than 10 ppm (0.001% by weight), the marking effect is not improved even if it exceeds 5% by weight. Therefore, addition of 5% by weight is sufficient. It is desirable to add a small amount to prevent unnecessary coloring of carbon when the product is formed.

When the water content of the polyamide resin of the present invention is less than 0.06% by weight, the effects of the present invention cannot be imparted even if water is contained. Further, if it exceeds 12% by weight, the mechanical properties of the polyamide resin are adversely affected. Therefore, addition of 12% by weight is sufficient, and in addition, deterioration of mechanical properties due to unnecessary moisture when forming a molded product is caused. In order to prevent it, it is desirable to add an appropriate amount.

If desired, the polyamide resin of the present invention may contain other polymers and additives such as stabilizers, colorants, ultraviolet absorbers, mold release agents, crystallization accelerators, and crystal nucleating materials, as long as the characteristics are not significantly impaired. , Granular or plate-like fillers, impact modifiers, flame retardants, reinforcing materials, antioxidants and the like may be contained.

The polyamide resin molded article of the present invention is adjusted to have an appropriate amount of water before or after molding. The polyamide resin can be obtained by various known manufacturing methods. Usually, it is preferable to disperse the resin and the compounding ingredients in the resin composition more uniformly, and all or a part of them are simultaneously or separately mixed, for example, in a blender, a kneader, a panbury mixer, a roll, an extruder or the like. The method of mixing and homogenizing can be used. Further, there is a method in which a dry-blended molding material is melt-kneaded with a heated extruder to homogenize it, then extruded into a wire shape, and then cut into a desired length to granulate.

The polyamide resin or resin composition of the present invention can be molded very easily by a conventional method using a general thermoplastic resin molding machine. The polyamide resin molded article of the present invention adjusted to the above water content is irradiated with a laser beam, and the portion irradiated with the laser beam clearly foams or decomposes to cause a peripheral laser beam non-irradiated portion. It has the property of showing clear contrast.

Therefore, by utilizing this property, the polyamide resin composition of the present invention can directly irradiate a laser beam to a molded article made of the polyamide resin composition of the present invention to form a desired printing or printing. it can. Further, a tag or plate made of the polyamide resin of the present invention is irradiated with laser light to give desired printing or printing, and thus the printing or printing of the tag or plate is applied to the molding to identify the molding. To be

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples. In addition,
The evaluation of various indexes in the examples was performed by the following methods.

The laser processing was performed by marking with a YAG laser (NEC laser marker SL475E2).

The marking property based on the contrast is evaluated by the difference in lightness (ΔL ^* ) between the surface of the molded product and the surface of the colored surface formed by laser light, the white index (WI) of the colored surface, the yellow index (YI) and the foaming state. It was evaluated by.

The color difference TC-
It was performed using 1800MK-II. Further, the foaming condition was confirmed by confirming whether uniform and fine foaming was formed. When uniform and fine foam was formed, it was represented by ⊚.

[Examples 1-9 and Comparative Examples 1-2] Table 1
And various raw materials shown in Table 2 are uniformly dry-blended in a predetermined amount ratio in advance, and then a cylinder temperature of 280 ° C. is measured by using a twin-screw extruder with a vent having a screw diameter of 44 mm.
300 ℃, screw rotation speed 160rpm, discharge rate 40k
After melt-kneading at g / h, the thread discharged from the die was cooled and then cut to obtain a molding pellet.

Then, using the pellets, a test piece for laser marking was molded in an injection molding machine having an injection capacity of 5 ounces under the conditions of an injection pressure of 800 kg / cm ² , a cooling time of 20 seconds, and a total molding cycle of 30 seconds. And subjected to laser marking.

[0025]

[Table 1]

[0026]

[Table 2]

The results of these experiments are shown in Tables 1 and 2.

The following various raw materials shown in Tables 1 and 2 were used.

-Nylon 46 (PA46) Teijin Ltd. KS200 Intrinsic viscosity: 1.2 Crystallinity: 60% -Nylon 6 (PA6) Teijin Ltd. Teijin Nylon NH-8001-Cabon black (CB) Denka Black Co., Ltd. Denka Black Average particle size: 42 mμ Purity: 99.8%

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the principle of a method of irradiating a surface of a molded product made of a polyamide resin of the present invention with a CO ₂ laser.

FIG. 2 is an explanatory diagram for explaining the principle of a method of irradiating the surface of a molded product made of the thermoplastic resin composition of the present invention with a YAG laser.

[Explanation of symbols]

 11 Folding mirror 12 Cylindrical lens 13 Stencil 14 Meniscus lens 15 Galvanometer 16 Laser head 17 Galvanometer 18 Focus lens

Claims (2)

[Claims] 1. 100 parts by weight of a polyamide resin having a water content of 0.06% to 12% by weight contains 0.001 to 5 parts of carbon.
A polyamide resin composition having excellent laser marking properties, which is obtained by blending parts by weight. 2. The polyamide resin composition according to claim 1, wherein the polyamide resin is nylon 6, nylon 66 or nylon 46.