WO1997001446A1

WO1997001446A1 - Use of polymer molding compounds to produce partial color change using laser energy to generate high-contrast optical information

Info

Publication number: WO1997001446A1
Application number: PCT/EP1996/002551
Authority: WO
Inventors: Aziz El Sayed; Frank Gerling; Salvatore Messina; Herbert Magerstedt; Karsten-Josef Idel; Edgar Ostlinning
Original assignee: Bayer Aktiengesellschaft
Priority date: 1995-06-26
Filing date: 1996-06-13
Publication date: 1997-01-16
Also published as: EP0835185A1; CA2225717A1; TW404963B; KR19990028386A; JPH11508202A; DE19523086A1

Abstract

The invention pertains to the use of polymer molding compounds composed of polymers selected from the group of polyamides, polyolefins, ABS-type graft polymer, polyacrylates, polymethacrylates or a mixture of polycarbonate, ABS-type graft polymer and optionally copolymer, carbon black, reinforcing materials, elastomer modifier, flame-protection additives and processing additives, to produce light or gray markings on a dark background using laser inscription, in particular to generate high-contrast optical information, for example letters, numbers, patterns and/or pictures, etc.

Description

USE OF POLYMER MOLDS FOR PARTIAL COLOR

CHANGE BY LASER ENERGY TO GENERATE

OPTICAL INFORMATION WITH HIGH CONTRASTS

The invention relates to the use of polymer molding compositions for partial color changes by laser energy, in particular for generating optical information, e.g. Letters, numbers, patterns and / or pictures etc. with very good contrasts.

The application of patterns, letters, numbers and / or images using a laser beam recorder to identify and decorate molded parts made of plastics is becoming increasingly important. In addition to being economical compared to conventional labeling methods, laser labeling offers great flexibility in terms of font, font size and font design, regardless of the lot size. Marking electrical / electronic

Components, keycaps, housings and ID cards are a classic application for laser marking.

The following options for marking plastics by means of laser marking are known.

1. Dark characters on a light background

A polymer matrix is colored with light colorants - pigments or dyes. In laser marking, the polymer matrix / colorant is partially carbonized by absorption of the laser energy. This creates a dark discoloration of the light polymer matrix. This behavior is limited to polymers that tend to carbonize.

The contrast ratios that can be achieved in this way are not sufficient for many areas of application. The addition of colorants which change their color due to absorption of the laser energy is described in EP-A 0 190 997. For example, Polybutylene terephthalate colored red with iron oxide. Laser marking creates dark characters on a red background. The

Contrast ratio has proven to be insufficient. 2. Bright characters on a dark background

Polymers, colorants or additives that tend to foam due to the absorption of laser energy have proven effective for this type of labeling. Foaming creates bright fonts on a dark background. The achievable contrast ratios are not sufficient for many areas of application.

The present invention relates to polymer molding compositions which, when the laser energy is absorbed, give bright characters on a dark background with a very high contrast ratio.

Surprisingly, it was found that by using very finely divided carbon black in the polymer matrix, bright characters on a dark background can be achieved by absorption of the laser energy. Different shades of gray can be obtained by changing the laser energy.

The invention relates to the use of polymer molding compositions consisting of:

A) 99.97 to 50, preferably 99.97 to 70 parts by weight of polymer selected from the group of polyamides. Polyolefins, graft polymer of the ABS type, polyacrylates, polymethacrylates or a mixture of polycarbonate, graft polymer of the ABS type and optionally

Copolymer,

B) 0.03 to 0.5, preferably 0.03 to 0.3 parts by weight of carbon black,

C) 0 to 50 parts by weight of reinforcing materials,

D) 0 to 20 parts by weight of elastomer modifier, E) 0 to 55 parts by weight of flame retardant additives and

F) 0 to 2 parts by weight of processing additives

for generating light or gray characters on a dark background using a laser beam.

Another object of the invention is the use of the colored polymers for the production of molded articles by means of laser beam recorders can be labeled, labeled or provided with visual representations.

The polymer moldings used according to the invention can be produced on commercially available single-shaft and twin-shaft extruders. The soot is dosed as a color concentrate. Commercially available injection molding machines can be used to produce the molded parts.

Thermoplastic polyamides suitable according to the invention are generally aliphatic polyamides or polyamides with a predominantly aliphatic content. Polyamide 6 or polyamide 66 or copolyamides of polyamide 6 with diamines (preferably C ₄ -C _{] 6} -, in particular C ₄ -C ₈ -alkylenediamines) and dicarboxylic acids (preferably C ₄ -C _{] 2} -, in particular C _{4, are} preferred -C ₈ -alkylene dicarboxylic acids) or polyamide 66 with a comonomer content of at most 20% by weight.

Polyolefins according to the invention are polymers of aliphatic unsaturated hydrocarbons, such as, for example, ethylene, propylene, butylene or isobutylene, which are obtained by customary processes, for example radical polymerization, and average weight-average molecular weights lvL _^ , (measured by gel chromatography methods) between 5,000 and have 3,000,000. Both high pressure polyolefin and low pressure polyolefin are useful. The unsaturated hydrocarbons can also be copolymerized in a known manner with other vinyl monomers such as, for example, vinyl acetate, acrylic acid or acrylic acid esters, the proportion of vinyl monomers being at most 30% by weight, preferably up to 25% by weight. Polyethylene and polypropylene are preferred.

As polymers of alkyl esters of (meth) acrylic acid are preferably those having a C _j _{-C] 8} alkyl ester used of the (meth) acrylic acid.

As esters of acrylic acid, the C _j _{-C] 8} alkyl ester are generally as Me¬ thyl-, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl , tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, lauryl or stearyl acrylate, preferably methyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate, and mixtures of these monomers , used.

The esters of methacrylic acid are generally the C 1 -C 4 -alkyl esters, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec.-butyl, tert. -Butyl-, Pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, lauryl or stearyl acrylate, preferably methyl methacrylate, and mixtures of these monomers are used.

Thermoplastic, aromatic polycarbonates suitable in accordance with the invention in a mixture with graft polymer and optionally copolymer are those based on the diphenols of the formula I.

^O

- ^O wherein A is a single bond, C _r C ₅ alkylene, C ₂ -C ₅ alkylidene, C ₅ -C ₆ cycloalkylidene, -S- or -SO ₂ -.

Suitable diphenols of the formula (I) are, for example, hydroquinone, resorcinol,

4,4'-dihydroxy diphenyl, 2,2-bis (4-hydroxyphenyl) propane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane or l, l-bis (4-hydroxyphenyl ) cyclohexane.

Preferred diphenols of the formula (I) are 2,2-bis (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) cyclohexane.

The diphenols of the formula (I) are either known from the literature or can be prepared by processes known from the literature.

The preparation of the polycarbonates suitable according to the invention is known from the literature and can be carried out, for example, with phosgene according to the interfacial process or with phosgene according to the process in a homogeneous phase (the so-called pyridine process), the molecular weight to be set in each case being known by a corresponding amount of known Chain breakers is achieved. Suitable chain terminators are, for example, monophenols such as phenol itself, p-cresol, p-tert-butylphenol and p-isooctylphenol.

The polycarbonates suitable according to the invention have average weight molecular weights

measured for example by ultracentrifugation or by scattered light measurement) from 10,000 to 200,000, preferably from 20,000 to 80,000. The polycarbonates suitable according to the invention are both homopolycarbonates and copolycarbonates.

The polycarbonates suitable according to the invention can be branched in a known manner, preferably by incorporating 0.05 to 2.0 mol%, based on the sum of the diphenols used, of three- or more than three-functional compounds, for example those with three or more than three phenolic OH groups.

Suitable graft polymers of the ABS type, alone or in a mixture with polycarbonate, are:

Graft polymers of a mixture of

K. l. 50 to 95, preferably 60 to 90, parts by weight of styrene, α-methylstyrene, halogen- or methyl-substituted styrene, C 1 -C ₈ -alkyl methacrylate, in particular methyl methacrylate, C _] -C ₈ -alkyl acrylate, in particular methacrylate, or mixtures of these compounds and

K.1.2 5 to 50, preferably 10 to 40, parts by weight of acrylonitrile, methacrylonitrile

C _j -C ₈ alkyl methacrylates, especially methyl methacrylate, C _j -C ₈ alkyl acrylate, especially methacrylate, maleic anhydride, C _j -C ₄ alkyl or phenyl-N-substituted maleimides or mixtures of these compounds

K.2 5 to 95, preferably 20 to 70, parts by weight of diene-based polymer with a glass transition temperature below -10 ° C.

Preferred graft bases are polybutadienes, butadiene / styrene copolymers and acrylate rubbers. The graft base is particulate and generally has an average particle diameter (d ₅₀ ) of 0.05 to 5 μm, preferably 0.1 to 0.8 μm.

In addition to butadiene, the graft base can contain up to 50% by weight of residues of other ethylenically unsaturated monomers, such as styrene, acrylonitrile, esters of acrylic or methacrylic acid with 1 to 4 carbon atoms in the alcohol component (such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate) , Vinyl ester and / or contain vinyl ether. The preferred graft base consists of pure polybutadiene.

Preferred graft polymers are e.g. Bases K.2 grafted with styrene and / or acrylonitrile and / or (meth) acrylic acid alkyl esters such as polybutadienes, butadiene / styrene copolymers, i.e. Copolymers of DE-OS 1 694 173

(= U.S. Patent 3,564,077); polybutadienes grafted with acrylic or methacrylic acid alkyl esters, vinyl acetate, acrylonitrile, styrene and / or alkylstyrenes, butadiene / styrene or butadiene / acrylonitrile copolymers, polyisobutene or polyisoprene, as described e.g. in DE-OS 2 348 377 (= US-PS 3 919 353) are described.

Since, as is well known, the graft monomers are not necessarily grafted completely onto the graft base in the graft reaction, graft polymers are also understood according to the invention to mean those products which are obtained by polymerizing the graft monomers in the presence of the graft base.

The average particle size d ₅₀ is the diameter above and below which 50% by weight of the particles lie. It can be determined by means of ultracentrifuge measurement (W. Scholtan, H. Lange, Kolloid, Z. and Z. Polymer 250 (1972), 782-796).

In the case of a mixture of polycarbonate, graft polymer of the ABS type and, if appropriate, copolymer, 50 to 96.5, in particular 60 to, are preferably used

96 parts by weight of polycarbonate, up to 25 parts by weight, in particular 3 to 15 parts by weight of graft polymer of the ABS type and optionally up to 40 parts by weight, in particular up to 20 parts by weight, of copolymer

50 to 95 wt .-% styrene, α-methylstyrene, nucleus-substituted styrene, methyl methacrylate or a mixture thereof, and

50 to 5 wt .-% (meth) acrylonitrile, methyl methacrylate or mixtures thereof

used. Carbon black B) of the molding compositions used according to the invention are very finely divided carbon blacks. The carbon black can be used as pure carbon black (particle size 13 to 20 nm), in pearl shapes or as a concentrate, for example in Microlen Schwarz ^B® from Ciba Geigy (Basel).

As reinforcement C) of the molding compositions used according to the invention are up to

50% by weight of commercially available glass fibers and / or mineral fibers and / or mineral fillers such as kaolin, wollastonite, talc or chalk are used.

Up to 20% by weight of commercially available EP (D) M rubbers, graft rubbers based on butadiene styrene, acrylonitrile (see above), acrylate rubbers, polyurethanes or EVA are used as elastomer modifier D) according to this invention. Copolymers with or without functional coupling groups are used.

Up to 55% by weight of commercially available organic compounds or halogen compounds with synergists or commercially available organic nitrogen compounds or organic / inorganic phosphorus compounds are used as flame retardant additives E) (e.g. EP-A 345 522, DE-OS 43 28 656). Also mineral

Flame retardant additives such as Mg hydroxide or Ca-Mg carbonate hydrate can be used.

The processing additives E) consist of up to 2% by weight of commercially available lubricants, stabilizers, mold release agents and nucleating agents.

Commercially available laser systems, preferably Nd-YAG solids, can be used as energy sources. The wavelength can be between 193 nm and 10600 nm, preferably 1064 nm.

The molding compositions used according to the invention can be used to apply optical information in the form of patterns, graphics, numbers, letters, characters, images (e.g. passport photos, portraits, photos) etc.

Laser energy, e.g. can be used by laser beam recorders.

For example, photographic images can be transferred to the molding compositions used according to the invention. Examples

The following products were used in the examples:

Polyamide 6 = Durethan B 3 ISK ^® from Bayer AG

Polyamide 6 glass fiber reinforced (30%) = Durethan BKV 30 H ^® from Bayer AG Polyamide 6 glass fiber reinforced (30%) impact resistant. = Durethan BKV 130 ^® the

Bayer AG

Polyamide 6 glass fiber reinforced (30%) with reduced water absorption - Durethan

RM KU 2-2501 ^® from Bayer AG

Polyamide 6 glass fiber and glass ball reinforced = Durethan BG 30 X ^® from Bayer AG Teilaromat. Polyamide = Durethan T 40 ^® from Bayer AG

ABS = Novodur P2H ^® from Bayer AG

ABS + polycarbonate flame retardant - Bayblend FR 90 ^®

PMMA = Plexiglas 7N ^® from Röhm GmbH Darmstadt

Carbon black Microlen Black B ^® / Ciba Geigy

The dyes were premixed with the granules and extruded and granulated using a twin-screw mixer. The granules obtained were injection-molded into plates on an Arburg injection molding machine and labeled with a FOBALLAS ND-YAG laser.

Depending on the intensity of the laser beam energy, white or gray characters are generated on a black background. All characters and symbols are characterized by very good contrasts with different shades of gray.

Table 1

Table 2

50% concentrate

Claims

claims

1. Use of polymer molding compounds

A) 99.97 to 50 parts by weight of polymer, selected from the group of polyamides, polyolefins, graft polymers of the ABS type, polyacrylates, polymethacrylates or a mixture of

Polycarbonate, graft polymer of the ABS type and, if appropriate, copolymer,

B) 0.03 to 0.5 part by weight of carbon black,

C) 0 to 50 parts by weight of reinforcing materials, D) 0 to 20 parts by weight of elastomer modifier,

E) 0 to 55 parts by weight of flame retardant additives and

F) 0 to 2 parts by weight of processing additives

for creating light or gray characters on a dark background using laser inscription.

2. Use according to claim 1, characterized in that it as

Contain polymeric polyamides.

3. Use according to claim 1, wherein 0.03 to 3 parts by weight of carbon black are used.

4. Use according to claim 1, characterized in that they contain 0 to 50 parts by weight of glass fibers, mineral fibers or mineral fillers as reinforcing materials.

5. Use according to claim 1, characterized in that they contain 0 to 40 parts by weight of EPM, EPDM, acrylic rubber or EVA copolymers as the elastomer modifier.

6. Use according to claim 1, characterized in that they contain as flame retardants 0 to 55 parts by weight of commercially available flame retardant additives based on organic halogen, nitrogen, phosphorus compounds, or Mg hydroxide, or Ca-Mg carbonate hydrate .

7. Use according to claim 1, characterized in that they contain 0 to 2% of lubricants, stabilizers, mold release agents and nucleating agents as processing additives.

8. Use according to claim 1 for the application of optical information by means of laser energy.

9. Images according to claims 1 and 8.

10. Passport picture, portrait, photo transferred according to claim 9.