JP2001080212A - Resin composition for laser marking and molding made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve laser marking properties by using a coloring agent master containing a graft copolymer of an unsaturated alkyl carboxylate monomer mixture and a carbon black having a mean particle size of specific numeric value ranges, respectively of specific wt.%, in a rubber-like polymer. SOLUTION: A thermoplastic resin of 100 pts.wt. is mixed with a coloring agent master of 0.05 to 5 pts.wt. obtained by melt kneading (I)+(II)+(III)=100 pts.wt. of a rubber-containing graft copolymer (I) of 40 to 80 pts.wt. obtained by blending a monomer mixture made of an unsaturated alkyl carboxylate monomer of 50 to 90 wt.% (b), an aromatic vinyl monomer of 0 to 20 wt.% (c) and a vinyl cyanide monomer of 0 to 20 wt.% (d) with a rubber-like polymer of 20 to 80 pts.wt., an unsaturated alkyl carboxylate copolymer (II) of 10 to 60 pts.wt. containing (b), (c) and (d) and a carbon black (III) having a mean particle size of 10 to 50 μm of 5 to 40 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a resin composition capable of giving a clear white marking upon irradiation with a laser beam, and a molded article comprising the same.

[0002]

2. Description of the Related Art Vinyl cyanide such as acrylonitrile and methacrylonitrile and styrene, α-
ABS resin copolymerized with two or more compounds selected from aromatic vinyl such as methylstyrene is excellent in impact resistance, mechanical strength, and moldability, and is suitable for use in OA equipment and home appliances. Widely used. Characters and the like are marked on such a molded product, and conventionally, printing using an ink such as silk printing or tampo printing has been mainly performed. However, in recent years, attention has been paid to the method of marking with a laser beam, which can be performed easily and efficiently.

[0003] As these technical methods, a method of blending carbon black or graphite with a material (Japanese Patent Application Laid-Open No. 57-116620) is a method of copolymerizing a (meth) acrylate ester monomer and a vinyl monomer. Method of blending coalesced with rubber-containing styrenic resin
(JP-A-8-112968) has been proposed.

[0004]

However, when carbon black is simply blended with a material, the laser light irradiated portion is immediately carbonized, and the marking portion is burnt, and the whiteness of the irradiated portion is reduced. Was. In the method of blending a copolymer comprising a (meth) acrylate ester monomer and a vinyl monomer with a rubber-containing styrene resin, there is a problem that the outline of a marking portion is blurred and lacks sharpness. .

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a coloring agent to be added to a styrenic resin in order to solve the above-mentioned problems. As a result, the unsaturated carboxylic acid alkyl ester monomer was added to the rubber polymer. By blending a graft copolymer obtained by grafting a monomer mixture containing and a carbon black having a specific particle size in a specific ratio and using a melt-kneaded colorant master, a clear white marking is exhibited. The inventors have found that the present invention can be performed, and have completed the present invention.

That is, the present invention relates to a rubbery polymer (a) 2
50 to 90% by weight of unsaturated carboxylic acid alkyl ester monomer (b), 10 to 50% by weight of aromatic vinyl monomer (c), and vinyl cyanide monomer based on 0 to 80 parts by weight (D) a monomer mixture consisting of 0 to 20% by weight
40 to 80 parts by weight of a rubber-containing graft copolymer (I), 50 to 90% by weight of an unsaturated carboxylic acid alkyl ester monomer (b), Unsaturated carboxylic acid alkyl ester-based copolymer (II) comprising 10 to 50% by weight of monomer (c) and 0 to 20% by weight of vinyl cyanide monomer (d)
(I) + (II) consisting of 5 to 40 parts by weight of carbon black (III) having an average particle diameter of 10 to 50 nm by weight.
+ (III) = 100 parts by weight of a colorant master (IV) obtained by melt-kneading 100 to 100 parts by weight of a thermoplastic resin (V) with respect to 0.05 to 5 parts by weight of a resin composition for laser marking And a molded article obtained by molding the composition, preferably by direct injection molding without melt-kneading with an extruder.

[0007]

Embodiments of the present invention will be described below.

The rubbery polymer (a) used in the rubber-containing graft copolymer (I) used in the present invention is a diene rubber, an acrylic rubber, an ethylene rubber or the like, and specifically, polybutadiene, Poly (butadiene-styrene), poly (butadiene-acrylonitrile), polyisoprene, poly (butadiene-butyl acrylate), poly (butadiene-methyl methacrylate), poly (butyl acrylate-methyl methacrylate), poly (butadiene- Ethyl acrylate), ethylene-propylene rubber, ethylene-propylene-diene rubber, poly (ethylene-isoprene), poly (ethylene-methyl acrylate) and the like. These rubbery polymers are used in one kind or in a mixture of two or more kinds. Among these rubbery polymers, polybutadiene, poly (butadiene-styrene), poly (butadiene-acrylonitrile) and ethylene-propylene rubber are preferably used in view of impact resistance.

The unsaturated carboxylic acid alkyl ester-based monomer (b) used in the rubber-containing graft copolymer (I) and the unsaturated carboxylic acid alkyl ester-based copolymer (II) in the present invention has 1 carbon atom. Acrylic esters and / or methacrylic esters having from 6 to 6 alkyl groups or substituted alkyl groups are preferred, and one or more of them can be used. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate,
N-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, (meth)
Examples thereof include n-hexyl acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, and 2-chloroethyl (meth) acrylate. Of these, methyl methacrylate is preferred.

Specific examples of the aromatic vinyl monomer (c) used in the rubber-containing graft copolymer (I) and the unsaturated carboxylic acid alkyl ester copolymer (II) in the present invention include styrene, α -Methylstyrene, orthomethylstyrene, paramethylstyrene, para-t-butylstyrene, halogenated styrene, and the like, and one or more kinds can be used. Styrene and α-methylstyrene are preferred, and styrene is more preferred.

Specific examples of the vinyl cyanide monomer (d) used for the rubber-containing graft copolymer (I) and the unsaturated carboxylic acid alkyl ester copolymer (II) in the present invention include acrylonitrile and methacrylic acid. Lonitrile and the like can be used, and one kind or two or more kinds can be used. Among them, acrylonitrile is preferred in terms of impact resistance.

The content of the rubbery polymer (a) in the rubber-containing graft copolymer (I) must be 20 to 80 parts by weight. If the amount is less than 20 parts by weight, the laser marking property is inferior, and if it exceeds 80 parts by weight, the dispersibility is reduced and the appearance of the molded article is deteriorated. Among them, 30 to 70 parts by weight is preferable.

The proportion of the unsaturated carboxylic acid alkyl ester monomer (b) in the monomer mixture in the rubber-containing graft copolymer (I) must be 50 to 90% by weight. . If it is less than 50% by weight, the laser marking property is inferior, and if it exceeds 90% by weight, the dispersibility is reduced and the appearance of the molded article is deteriorated. Especially, 60-80 weight% is preferable.

The proportion of the aromatic vinyl monomer (c) in the monomer mixture in the rubber-containing graft copolymer (I) must be 10 to 50% by weight. 1
If it is less than 0% by weight, the dispersibility decreases, and the appearance of the molded product is poor.
If it exceeds 50% by weight, the laser marking property is inferior. Among them, 20 to 40% by weight is preferable.

The vinyl cyanide monomer (d) in the monomer mixture of the rubber-containing graft copolymer (I)
Is required to be 0 to 20% by weight. 2
If it exceeds 0% by weight, the laser marking property is inferior. Among them, 0 to 10% by weight is preferable.

The unsaturated carboxylic acid alkyl ester copolymer (II) in the present invention comprises 50 to 90% by weight of the unsaturated carboxylic acid alkyl ester monomer (b) and the aromatic vinyl monomer (c). The amount is 10 to 50% by weight and the vinyl cyanide monomer (d) is 0 to 20% by weight. 50% by weight of unsaturated carboxylic acid alkyl ester monomer (b)
If it is less than 90%, the laser marking property is inferior.

The aromatic vinyl monomer (c) is 10
When the amount is less than 50% by weight, the dispersibility decreases, and the appearance of the molded product is poor. When the amount exceeds 50% by weight, the laser marking property is poor.

Further, when the vinyl cyanide monomer (d) is 2
If it exceeds 0% by weight, the laser marking property is inferior. Among them, unsaturated carboxylic acid alkyl ester monomers (b)
60 to 80% by weight, aromatic vinyl monomer (c) 20 to
It is preferably 40% by weight and 0 to 10% by weight of a vinyl cyanide monomer (d).

Carbon black (III) in the present invention
Examples thereof include thermal black, furnace black, and channel black.
It is indispensable to use one having a thickness of ５０50 nm. 1
If it is less than 0 nm, the cohesive force between the carbon blacks is so high that they cannot be sufficiently dispersed and the appearance of the molded article is poor. If it exceeds 50 nm, the laser energy cannot be absorbed uniformly by the molded article, (Laser marking property) is inferior. Especially, it is preferably 10 to 40 nm, more preferably 10 to 30 nm.

The colorant master of the present invention comprises (I) + (II)
+ (III) = 100 parts by weight, and the compounding ratio is 40 to 80 parts by weight of the rubber-containing graft copolymer (I) and 10 to 60 parts of the unsaturated carboxylic acid alkyl ester-based copolymer (II).
Parts by weight, 5 to 40 parts by weight of carbon black (III). If the amount of the rubber-containing graft copolymer (I) is less than 40 parts by weight, clear laser marking cannot be performed.
If the amount exceeds 0 parts by weight, the dispersibility of carbon is reduced, and the appearance of a molded product is deteriorated. If the amount of the unsaturated carboxylic acid alkyl ester-based copolymer (II) is less than 10 parts by weight, clear laser marking cannot be performed. If the amount exceeds 60 parts by weight, the dispersibility of carbon is reduced and the appearance of a molded product is poor. Become. If the amount of carbon black (III) is less than 5 parts by weight, clear laser marking cannot be performed, and if it exceeds 40 parts by weight, the dispersibility of carbon is reduced and the appearance of a molded article is deteriorated.

As the thermoplastic resin (V) of the present invention, AB
Examples include S resin, PS resin, HIPS resin, PMMA resin, and transparent ABS resin, and a thermoplastic resin containing methyl methacrylate is preferred. Specifically, the content of PMMA resin and methyl methacrylate is 50 wt% or more. Transparent ABS resin is more preferred.

The method for producing the copolymers (I) and (II) may be any of polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization, and is not particularly limited. There is also no particular limitation on the method of charging the monomer, and the initial batch charging, or while charging a part or all of the charged monomer continuously or divided to suppress the generation of the composition distribution of the copolymer. It may be polymerized.

The method for producing the colorant master (IV), the thermoplastic resin (V), and the resin composition for laser marking according to the present invention is, for example, melt kneading with a Banbury mixer, a roll, and a single or multi-screw extruder. Various methods can be employed.

In the present invention, the ratio of the colorant master (IV) is 0.05 to 100 parts by weight of the thermoplastic resin (V).
-5 parts by weight. If the amount is less than 0.05 parts by weight, laser energy cannot be efficiently absorbed, and clear marking cannot be performed. If the amount exceeds 5 parts by weight, not only the impact strength of the molded product is deteriorated, but also the laser energy is excessively absorbed, and the whiteness is deteriorated. Among them, 0.3 to 1 part by weight is preferable.

The laser beam of the present invention is an excimer laser,
Nitrogen laser, YAG laser, crystal laser,
Marking can be performed using a known laser beam such as a CO ₂ laser.

The resin composition for laser marking of the present invention is molded by a known method currently used for molding thermoplastic resins such as injection molding, extrusion molding, blow molding, vacuum molding, compression molding, gas assist molding and the like. Although not particularly limited, preferably, a blend of the thermoplastic resin (V) and the colorant master (IV) is
Direct injection molding without melt-kneading in an extruder.

The applications of these molded articles are as follows:
Although there are no particular restrictions on electronics, automobiles, machines, miscellaneous goods, etc., the characteristics of the molded article of the present invention are effective for applications in which characters and symbols are printed and displayed. Above all, it prints and displays the housing parts of OA equipment, electrical and electronic products, structural parts of refrigerators, miscellaneous goods such as pachinko trays, sanitary uses such as toilets and kitchens, and interior and exterior materials for automobiles. Can be applied to the site. [Measurement Method of Physical Properties] A method for measuring properties relating to the resin composition for laser marking of the present invention is described below. For general properties such as laser marking property and impact resistance, test pieces were molded by injection molding and measured according to the following test methods. (1) Rubber weight average particle diameter "Rubber Age Vol.88 p.484-
490 (1960) by E.I. Schmidt, P .;
H. Sodium alginate method described in "Biddison" (using the fact that the particle size of polybutadiene to be creamed varies depending on the concentration of sodium alginate, the particles having a cumulative weight fraction of 50% from the cumulative weight fraction of the creamed weight ratio and the sodium alginate concentration) Find the diameter). (2) Graft ratio Acetone was added to a predetermined amount (m) of the graft copolymer, and the mixture was refluxed for 3 hours. p. m. (1000
After centrifugation at 0 G) for 40 minutes, the insoluble matter was filtered, and the insoluble matter was dried under reduced pressure at 60 ° C. for 5 hours, and the weight (n) was measured. The graft ratio was calculated from the following equation. Here, L is the rubber content of the graft copolymer.

Graft ratio (%) = ｛[(n)-(m) ×
L] / [(m) × L]｝ × 100 (3) Primary Average Particle Diameter of Carbon Black Individual primary particle diameters (major diameters) were directly measured from a carbon black photograph by a transmission electron microscope (TEM). . The photographic magnification was 100,000, and the measurement was performed statistically. Therefore, 1000 or more primary particles were measured and calculated by arithmetic mean.

(4) Laser Marking Property The measurement sample was marked at a wavelength of 1064 nm with a YAG laser (“Scriba2” manufactured by Electrox) and measured.

Whiteness: The whiteness index of the laser mark portion was measured using a color computer ("Caracom System") manufactured by Dainichi Seika Kogyo Co., Ltd., using a whiteness index WI.

Clarity: The part marked with a laser is visually judged, and a thin line is clearly marked, and the contrast between the base color and the marking character color is good (O), and the bad one is (X). did. (5) Flowability (MFR): ISO1133 (220 ° C,
98N load). (6) Impact resistance (Izod impact): ASTM D256
(12.7mm notched, 23 ° C).

[0032]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to these embodiments. Reference Example 1 Production of Rubber-Containing Graft Copolymer (I) A1 A reactor purged with nitrogen was charged with 120 parts of pure water and 0.5 part of glucose.
Part, sodium pyrophosphate 0.5 part, ferrous sulfate 0.0
05 parts and 50 parts (in terms of solid content) of polybutadiene latex having a weight average particle diameter of 0.2 μm were charged, and the temperature in the reactor was raised to 65 ° C. while stirring. When the internal temperature reached 65 ° C., polymerization was started, and a mixture of 36 parts of methyl methacrylate, 12 parts of styrene, 2 parts of acrylonitrile and 0.3 part of t-dodecylmercaptan was continuously dropped over 5 hours. At the same time, an aqueous solution consisting of 0.25 parts of cumene hydroperoxide, 2.5 parts of potassium oleate and 25 parts of pure water was continuously added dropwise over 7 hours to complete the reaction. The obtained rubber-containing graft copolymer latex was coagulated with sulfuric acid, neutralized with caustic soda, washed, filtered and dried to obtain a rubber-containing graft copolymer (I) A1. Table 1 shows the graft ratio of the rubber-containing graft copolymer (I) A1. Reference Example 2 Production of Rubber-Containing Graft Copolymer (I) A2 In Reference Example 1, 36 parts of styrene and 14 parts of acrylonitrile were used, and polymerization was carried out in the same manner as in Reference Example 1. The described rubber-containing graft copolymer (I) A2 was obtained. Reference Example 3 Production of Unsaturated Alkyl Carboxylic Acid Copolymer (II) B1 In a stainless steel autoclave having a capacity of 20 L and equipped with a baffle and a Fowler-type stirring blade, a methyl methacrylate / acrylamide copolymer (special) was prepared. Kosho 45-2415
A solution of 0.05 part in 165 parts of ion-exchanged water was stirred at 400 rpm, and the inside of the system was replaced with nitrogen gas. Next, 72 parts of methyl methacrylate, styrene 2
A mixed solution of 4 parts, 4 parts of acrylonitrile, 0.2 part of t-dodecylmercaptan, and 0.4 part of 2,2′-azobisisobutyronitrile was added while stirring the reaction system,
The temperature was raised to 60 ° C. to initiate polymerization. After raising the reaction temperature to 65 ° C over 15 minutes, the temperature was raised to 100 ° C over 50 minutes. Thereafter, the reaction system is cooled, the polymer is separated, washed, and dried according to a usual method, and the unsaturated carboxylic acid alkyl ester copolymer (II) shown in Table 2 is used.
B1 was obtained. [Reference Example 4] Production of unsaturated carboxylic acid alkyl ester copolymer (II) B2 Among the conditions of Reference Example 3, 60 parts of methyl methacrylate was used.
Polymerization was carried out in the same manner as in Reference Example 5, except that 30 parts of styrene and 10 parts of acrylonitrile were used, and the unsaturated carboxylic acid alkyl ester copolymer (II) B shown in Table 2 was used.
2 was obtained. Reference Example 5 Production of Unsaturated Carboxylic Acid Alkyl Ester Copolymer (II) B3 The conditions of Reference Example 3 were changed except that methyl methacrylate was 5 parts, styrene was 90 parts, and acrylonitrile was 5 parts. Polymerization was carried out in the same manner as in Reference Example 5, and the unsaturated carboxylic acid alkyl ester-based copolymer (II) B3 shown in Table 2 was used.
I got [Reference Example 6] Carbon black (III) D1: Carbon black having a primary average particle diameter of 8 nm D2: Carbon black having a primary average particle diameter of 16 nm (Mitsubishi Chemical Corporation's Mitsubishi Carbon Black # 960) D3: 1 Carbon black having a secondary average particle size of 24 nm (Mitsubishi Chemical Corporation Mitsubishi Carbon Black # 44) D4: carbon black having a primary average particle size of 84 nm (Mitsubishi Chemical Corporation Mitsubishi Carbon Black # 10)

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4] Examples 1-28, Comparative Examples 1-22 Each of the copolymers produced in Reference Examples 1-5 and carbon black were mixed in a Henschel mixer at the mixing ratios shown in Tables 3 and 4, and then a 30 mmφ twin screw extruder was used. To obtain a colorant master (IV). Further, after mixing the colorant master (IV) and the thermoplastic resin (V) in a blending ratio shown in Tables 5 and 6, using a blender, the mixture was mixed at 40 mmφ.
It was extruded with a single screw extruder to obtain a resin composition for laser marking, and injection molded to obtain a test piece for evaluation. Also, the colorant master (IV) and the thermoplastic resin (V) were mixed in a blending ratio shown in Tables 5 and 6 by a blender and directly injection-molded without melt-kneading by an extruder for evaluation. I got a test piece. The evaluation results are as shown in Tables 5 and 6.

[0037]

[Table 5]

[0038]

[Table 6] Tables 5 and 6 show that the resin composition for laser marking of the present invention has excellent laser marking properties.

[0039]

The resin composition or molded article for laser marking according to the present invention has excellent laser marking properties and does not impair the molding processability and impact resistance of the base thermoplastic resin (V). It is suitable for parts displaying symbols and the like.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 53/02 C08L 53/02 // B41J 2/44 B41J 3/00 Q F term (reference) 2C362 CB67 2H111 HA14 HA23 HA32 4F071 AA10X AA22X AA33 AA33X AA34X AA76 AA77 AB03 AH19 BA01 BB05 BC03 4J002 BC031 BC041 BC073 BG061 BN151 BN152 DA036 FD016 GT00

Claims (5)

[Claims] 1. An unsaturated carboxylic acid alkyl ester monomer (b) 50 to 90% by weight and an aromatic vinyl monomer (c) based on 20 to 80 parts by weight of a rubbery polymer (a).
A monomer mixture consisting of 10 to 50% by weight and 0 to 20% by weight of a vinyl cyanide monomer (d);
40 to 80 parts by weight of the rubber-containing graft copolymer (I), 50 to 90% by weight of the unsaturated carboxylic acid alkyl ester monomer (b), and the aromatic vinyl monomer ( c) 10 to 60 parts by weight of an unsaturated carboxylic acid alkyl ester copolymer (II) composed of 10 to 50% by weight and 0 to 20% by weight of a vinyl cyanide monomer (d), and having an average particle diameter of 10 to 10%. (I) + (II) + (I) comprising 5 to 40 parts by weight of carbon black (III) having a thickness of 50 nm.
II) = 100 parts by weight of the colorant master (IV) obtained by melt-kneading the thermoplastic resin (V) with respect to 0.05 to 5 parts by weight.
A resin composition for laser marking obtained by mixing 100 parts by weight. 2. The resin composition for laser marking according to claim 1, wherein the unsaturated carboxylic acid alkyl ester monomer (b) is methyl methacrylate. 3. The resin composition for laser marking according to claim 1, wherein the thermoplastic resin (V) is a thermoplastic resin containing methyl methacrylate. 4. A molded article obtained by molding the resin composition for laser marking according to claim 1. 5. The thermoplastic resin (V) according to claim 1,
A molded product obtained by directly injection molding a compound of the colorant master (IV) without melt-kneading with an extruder.