# US 7,744,804 B2 · Laser-transmissible composition and method of laser welding

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- Number: US 7,744,804 B2
- Document ID: US7744804B2
- Status: Granted
- Kind: B2
- Application number: 11/073,731
- Filed: 2005-03-08
- Published: 2005-09-15
- Granted: 2010-06-29
- Earliest claimed: 2004-03-12
- Assignees: Orient Chemical Industries, Ltd.
- Inventors: Osamu Nakagawa; Makiko Matsui
- Web page: https://patentgrep.com/patent/US7744804B2

## CPC

- B29C 65/168: {placed at the interface}
- B29C 65/1635: {at least passing through one of the parts to be joined, i.e. laser transmission welding}
- B29C 65/1654: {scanning at least one of the parts to be joined}
- B29C 65/1667: {at the same time, i.e. simultaneous laser welding}
- B29C 65/1677: {making use of an absorber or impact modifier}
- B29C 65/1683: {coated on the article}
- B29C 66/1122: {Single lap to lap joints, i.e. overlap joints (B29C66/45, B29C66/472, B29C66/52272 take precedence)}
- B29C 66/1282: {comprising at least one overlap joint-segment}
- B29C 66/12841: {comprising at least two butt joint-segments}
- B29C 66/14: {the joint having the same thickness as the thickness of the parts to be joined (B29C66/1142 takes precedence)}
- B29C 66/43: {Joining a relatively small portion of the surface of said articles (B29C66/45 takes precedence)}
- B29C 66/71: {characterised by the composition of the plastics material of the parts to be joined (welding bar compositions B29C65/125)}
- B29C 66/73115: {Melting point}
- B29C 66/73752: {the to-be-joined areas of both parts to be joined being uncured}
- B29C 66/73921: {characterised by the materials of both parts being thermoplastics}
- C08K 5/0041: {Optical brightening agents, organic pigments}
- B29C 65/1616: {Near infrared radiation [NIR], e.g. by YAG lasers}
- B29C 65/1645: {heating both sides of the joint, e.g. by using two lasers or a split beam}
- B29C 65/1674: {making use of laser diodes (B29C65/167 takes precedence)}
- B29C 65/1696: {making use of masks}
- B29C 65/8207: {by mechanical methods}
- B29C 65/8215: {Tensile tests}
- B29C 65/8253: {by the use of waves or particle radiation, e.g. visual examination, scanning electron microscopy, or X-rays (B29C65/8292 takes precedence)}
- B29C 66/7212: {characterised by the composition of the fibres}
- B29C 66/73151: {Hardness}
- B29C 66/73152: {of different hardness, i.e. the hardness of one of the parts to be joined being different from the hardness of the other part}
- B29C 66/73321: {both parts to be joined being coloured}
- B29C 66/836: {Moving relative to and tangentially to the parts to be joined, e.g. transversely to the displacement of the parts to be joined, e.g. using a X-Y table (B29C66/65 takes precedence)}
- B29K 2023/00: Use of polyalkenes {or derivatives thereof} as moulding material
- B29K 2023/083: {EVA, i.e. ethylene vinyl acetate copolymer}
- B29K 2023/086: {EVOH, i.e. ethylene vinyl alcohol copolymer}
- B29K 2101/12: Thermoplastic materials
- B29K 2105/06: containing reinforcements, fillers or inserts
- B29K 2307/00: Use of elements other than metals as reinforcement
- B29K 2309/08: Glass
- B29K 2995/0022: Bright, glossy or shiny surface
- B29K 2995/003: Reflective
- B29K 2995/007: Hardness
- B29K 2995/0073: smooth
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS

## Abstract

A laser-transmissible composition comprises: a dynamic crosslinking polyolefin thermoplastic elastomer that has a melting point ranging from 160 to 210 degrees Centigrade in case of non-coloring, and dye salt exhibiting transmission of a laser having a wavelength of 800 to 1200 nm. A method for laser welding comprises: putting a laser-transmissible molded workpiece 1 made from the laser-transmissible composition onto a laser-absorptive molded workpiece 2 having a laser-absorbent 7, irradiating laser 3 towards the laser-transmissible molded workpiece 1 to weld the laser-transmissible molded workpiece 1 and the laser-absorptive molded workpiece 2.

## Claims

### Claim 1

A method for laser welding comprising:
preparing a dynamic crosslinking polyolefin thermoplastic elastomer in the presence of a metallocene catalyst including, as a main component, an ethylene-alpha-olefin random copolymer elastomer with a ratio of ethylene to alpha-olefin between 55:45 to 80:20 by weight, the dynamic crosslinking polyolefin thermoplastic elastomer having a melting point ranging from 160 to 210 degrees Centigrade;
dynamically crosslinking the dynamic crosslinking polyolefin thermoplastic elastomer with a crosslinking agent;
providing a laser energy-transmissible molded workpiece comprising a laser energy-transmissible composition comprising the dynamic crosslinking polyolefin thermoplastic elastomer and a dye salt capable of transmitting laser energy having a wavelength of 800 to 1200 nm, wherein the dye salt comprises an anion of an acid dye and a cation of an organic amine and the dye salt is selected from the group consisting of a monoazo dye salt, a disazo dye salt, an anthraquinone dye salt, an anthrapyridone dye salt, and a triphenylmethane dye salt;
providing a laser energy-absorptive molded workpiece comprising a composition comprising a thermoplastic polypropylene resin and a laser energy-absorbent including carbon black;
placing the laser energy-transmissible molded workpiece
irradiating a laser towards the laser energy-transmissible molded workpiece to weld the laser energy-transmissible molded workpiece to the laser energy-absorptive molded workpiece.

### Claim 2 (depends on 1)

The method for laser welding according to claim 1, wherein the laser energy-transmissible molded workpiece is placed onto the laser energy-absorptive molded workpiece through an applied layer which includes the laser energy-absorbent.

### Claim 3 (depends on 1)

The method for laser welding according to claim 1, wherein the laser energy-absorptive molded workpiece comprises a composition further including a dynamic crosslinking polyolefin thermoplastic elastomer.

### Claim 4 (depends on 1)

The method for laser welding according to claim 1, wherein the thermoplastic polypropylene resin includes talc.

### Claim 5 (depends on 1)

The method for laser welding according to claim 1, wherein the laser is irradiated by scanning, and thereby supplying a quantity of heat: K(J/mm2) to a surface of the laser energy-absorptive molded workpiece, said quantity of heat corresponding to the following numerical expression (I):
K=(p×T)/(100×q×d)≧0.5 (I)
wherein p(W) is an output of the laser, T(%) is a transmittance of the laser energy-transmissible molded workpiece under irradiation of the laser, q(mm/sec.) is a scanning speed of the laser, and d(mm) is the diameter of a spot of the laser irradiating onto the surface.

### Claim 6 (depends on 1)

The method for laser welding according to claim 1, wherein the dynamic crosslinking polyolefin thermoplastic elastomer exhibits a compressive strain ranging from 20 to 70% at 100 degrees Centigrade in accordance with Japanese Industrial Standard K-6262-1997.

### Claim 7 (depends on 1)

The method for laser welding according to claim 1, wherein the dynamic crosslinking polyolefin thermoplastic elastomer has a Shore hardness between 60 and 90 (A).

### Claim 8 (depends on 1)

The method for laser welding according to claim 1, wherein the dynamic crosslinking polyolefin thermoplastic elastomer in the laser energy-transmissible molded workpiece has an optical density of at least 1.5 with less than 0.1% of additive content thereof by weight.

### Claim 9 (depends on 1)

The method for laser welding according to claim 1, wherein the organic amine is selected from the group consisting of alicyclic amine and guanidine derivative.

### Claim 10 (depends on 9)

The method for laser welding according to claim 9, wherein the guanidine derivative is selected from the group consisting of 1,3-diphenylguanidine, 1-o-tolylguanidine, and di-o-tolylguanidine.

### Claim 11 (depends on 1)

The method for laser welding according to claim 1, wherein the carbon black has a primary particle size between 18 and 30 nm.

### Claim 12 (depends on 1)

The method for laser welding according to claim 1, wherein the laser energy-absorbent further includes nigrosine dyestuff.

### Claim 13 (depends on 1)

The method for laser welding according to claim 1, wherein the crosslinking agent is selected from the group consisting of an organic peroxide, a phenol resin compound, a quinoid compound, a sulfur compound and a bismaleimide compound.