Method and apparatus for providing foaming thermoplastic compositions

• US 4,549,915 A
• Filed: 01/11/1984
• Issued: 10/29/1985
• Est. Priority Date: 05/14/1982
• Status: Expired due to Fees

• Current Assignee: Bostik Incorporated (Totalenergies Se)
• Original Assignee: USM Corporation
• Inventors: Ritschel, Peter, Hartmann, Waldemar, Freudenreich, Herbert
• Primary Examiner(s): Dawson, Robert A.
• Application Number:
  US06/579,892
• Time in Patent Office: 657 Days
• Field of Search: l56/78, l56/291, 425/376 R, 425/377, 425/378 R, 428/317.5, 261/DIG. 26, 264/57, 427/207.1, 427/208.2, 427/244
• US Class Current: 156/78
• CPC Class Codes: B05B 7/0025 with a compressed gas supply
• CPC Class Codes: B05B 7/1272 actuated by gas involved in spraying, i.e. exiting the nozzle, e.g. as a spraying or jet shaping gas
• CPC Class Codes: B05B 7/1686 involving vaporisation of the material to be sprayed or of an atomising-fluid-generating product
• CPC Class Codes: B29B 7/7409 with supply of gas
• CPC Class Codes: B29B 7/7428 Methodical aspects
• CPC Class Codes: B29B 7/7457 Mixing heads without moving stirrer B29B7/7438, B29B7/76 take precedence
• CPC Class Codes: B29C 44/022 Foaming unrestricted by cavity walls, e.g. without using moulds or using only internal cores
• CPC Class Codes: B29C 44/1228 Joining preformed parts by the expanding material
• CPC Class Codes: B29C 44/1285 the preformed part being foamed
• CPC Class Codes: B29C 44/3446 Feeding the blowing agent
• CPC Class Codes: B29K 2077/00 Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2101/12 Thermoplastic materials
• CPC Class Codes: B29K 2105/0094 having particular viscosity
• CPC Class Codes: B29K 2105/0097 Glues or adhesives, e.g. hot melts or thermofusible adhesives
• CPC Class Codes: B29K 2223/083 EVA, i.e. ethylene vinyl acetate copolymer
• CPC Class Codes: B29K 2625/06 PS, i.e. polystyrene
• CPC Class Codes: B29K 2711/14 Wood, e.g. woodboard or fibreboard
• CPC Class Codes: B29K 2995/0097 Thickness
• CPC Class Codes: B29L 2031/26 Sealing devices, e.g. packaging for pistons or pipe joints
• CPC Class Codes: C08J 2203/10 Water or water-releasing compounds
• CPC Class Codes: C08J 2207/02 : Adhesive
• CPC Class Codes: C08J 2323/08 : Copolymers of ethene C08J2323/16 takes precedence
• CPC Class Codes: C08J 2331/04 : Homopolymers or copolymers of vinyl acetate
• CPC Class Codes: C08J 2377/00 : Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain of polyhydrazides C08J2379/06; of polyamide-imides or polyamide acids C08J2379/08; Derivatives of such polymers
• CPC Class Codes: C08J 9/125 : Water, e.g. hydrated salts
• CPC Class Codes: C09J 5/08 : using foamed adhesives
• CPC Class Codes: Y10T 428/249984 : Adhesive or bonding component contains voids

Abstract

Method and apparatus for providing a foamed mass of thermoplastic, e.g., a hot melt adhesive on a substrate by introducing a foaming agent to the composition which has been melted by heating in excess of 100° C. The foaming agent is provided by water entrained in a carrier gas and is preferably introduced to the thermoplastic as it is dispensed from an applicator. The invention permits foaming of adhesives using readily available raw materials and simple equipment readily derivable from existing hot melt adhesive applicators.

Claims

1. A method of providing a foamed mass for use in an adhesive bonding or sealing process in which a thermoplastic composition is melted by heating to a temperature in excess of 100°

C. and expelled through a nozzle from an applicator in admixture with a foaming agent characterized in that the foaming agent is water which is entrained in a stream of carrier gas and injected into the thermoplastic composition as it passes through the nozzle and is thereby distributed throughout the melted composition as it is expelled from the applicator.

2. A method according to claim 1 further characterised in that the expelled composition is deposited on a substrate and is allowed to foam freely under atmospheric pressure.

3. A method according to claim 1 or claim 2 further characterized in that the thermoplastic composition is brought to a viscosity no greater than about 1,500 mPas for introduction of the foaming agent.

4. A method according to claim 1 or claim 2 further characterized in that the thermoplastic composition and water are employed in a ratio by weight in the range 3.3:

1 to 10;

1 and the carrier gas is air under pressure.

5. A method according to claim 1 or claim 2 wherein the thermoplastic material is dispensed at a rate of between about 100 g/min and about 200 g/min.

6. A method according to claim 1 or claim 2 further characterized in that the thermoplastic composition is an adhesive or sealant composition of melting point about 68°

C. and comprising ethylene vinyl acetate copolymer, and the carrier gas is air at a pressure of 0.8 to 3.0 bar.

7. A method according to claim 1 or claim 2 further characterized in that the thermoplastic composition is an adhesive or sealant composition of melting point in the range of about 95°

C. to about 165°

C. comprising ethylene vinyl acetate copolymer, or a copolyamide and the carrier gas is air at a pressure of 1.5 to 3.0 bar.

8. A method of claim 1 or claim 2 further including the step of pressing a second substrate against the foamed mass to form an adhesive bond.

9. A method according to claim 8 wherein at least one of the substrates comprises foamed polystyrene, or chipboard.

10. An applicator device suitable for providing and applying a foamed adhesive mass comprising a heat conductive body portion having a melt supply passageway to provide communication between a source of melted thermoplastic composition and a nozzle orifice from which the composition is to be expelled, a valve element arranged for closing the nozzle orifice to control outflow of adhesive therefrom, characterized in that a gas supply passageway is located within the valve element to provide communication between sources of water and carrier gas and the nozzle orifice, and in having means for controlling the quantity of water supplied to the carrier gas and means for controlling the pressure of the carrier gas supply, the construction and arrangement being such that upon relative movement between the valve element and nozzle orifice to permit outflow of thermoplastic composition from the orifice, water and carrier gas may be fed under pressure to the composition flowing out through the nozzle and is distributed throughout the melted composition to provide a foamed mass upon expulsion from the applicator.

11. A device according to claim 10 further characterised in that pneumatic means is provided for controlling relative movement between the valve element and nozzle orifice.