WO2005087889A1 - Adhesive composition - Google Patents

Adhesive composition Download PDF

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Publication number
WO2005087889A1
WO2005087889A1 PCT/SG2004/000059 SG2004000059W WO2005087889A1 WO 2005087889 A1 WO2005087889 A1 WO 2005087889A1 SG 2004000059 W SG2004000059 W SG 2004000059W WO 2005087889 A1 WO2005087889 A1 WO 2005087889A1
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WO
WIPO (PCT)
Prior art keywords
adhesive composition
composition according
titanium dioxide
adhesive
filler
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Application number
PCT/SG2004/000059
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French (fr)
Inventor
Siew Puat Yeo
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Siew Puat Yeo
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Priority to PCT/SG2004/000059 priority Critical patent/WO2005087889A1/en
Publication of WO2005087889A1 publication Critical patent/WO2005087889A1/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J109/00—Adhesives based on homopolymers or copolymers of conjugated diene hydrocarbons
    • C09J109/06—Copolymers with styrene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/62—Polymers of compounds having carbon-to-carbon double bonds
    • C08G18/6212—Polymers of alkenylalcohols; Acetals thereof; Oxyalkylation products thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
    • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
    • C08G18/7657—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
    • C08G18/7664—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/04—Non-macromolecular additives inorganic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J113/00—Adhesives based on rubbers containing carboxyl groups
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J129/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Adhesives based on hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Adhesives based on derivatives of such polymers
    • C09J129/02—Homopolymers or copolymers of unsaturated alcohols
    • C09J129/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
    • C09J175/04—Polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2170/00—Compositions for adhesives
    • C08G2170/80—Compositions for aqueous adhesives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/10—Metal compounds
    • C08K3/11—Compounds containing metals of Groups 4 to 10 or of Groups 14 to 16 of the Periodic Table
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
    • C08L2666/54—Inorganic substances

Definitions

  • the present invention relates to an adhesive composition, to the preparation of the composition, to uses of the composition, and to products of such use. It is particularly but not . exclusively concerned with adhesive compositions for wood and wood-based materials .
  • Exemplary compositions include wood glues, wood sealers, putties, wood surface reinforcing agents, and impregnants for paper or card.
  • the present compositions find particular, but not exclusive, use as adhesives and binding, coating and sealing materials. They may be used in producing ⁇ modified woods' .
  • the invention provides a new use for titanium dioxide (Ti0 2 ) .
  • Component A contains: (Ai) a solution or dispersion comprising a polymer containing units having hydroxyl groups, and (Aii) a polymer derived from an optionally substituted styrene monomer, said polymer containing units having carboxyl groups.
  • Component B comprises (Bi) a polyfunctional aziridine crosslinker capable of crosslinking with at least one carboxyl group and at least one hydroxyl group.
  • the component A includes polymers containing acetate groups, e.g. polyvinyl acetate homopolymers or copolymers, (e.g. an ethylene vinyl acetate copolymer or terpolymer) , preferably as a dispersion with polyvinyl alcohol.
  • the composition may contain a filler, for improving water resistance.
  • Talc, silica, kaolin and calcium carbonate are exemplified.
  • US-A-3,931,088 (assigned to Kuraray Co., Ltd.) discloses an adhesive composition comprising (1) an aqueous solution of polyvinyl alcohol and (2) a hydrophobic solution of a polyisocyanate compound.
  • Preferred further ingredients include an aqueous emulsion of vinyl acetate polymer and/or an aqueous latex of butadiene polymer such as an aqueous latex of a copolymer of styrene and butadiene or an aqueous latex of a copolymer of acrylonitrile and butadiene.
  • fillers include organic substances such as wood powder and powder of walnut shell, etc., as well as inorganic substances, such as clay, kaolin and talc, etc.”
  • suitable fillers include organic substances such as wood powder and powder of walnut shell, etc., as well as inorganic substances, such as clay, kaolin and talc, etc.”
  • the effect of the filler is stated to be: “not only to prevent excessive penetration of adhesive into the wood, but also to impart better water resistance and initial adhesive strength by reacting with the isocyanate”.
  • illers include calcium carbonate (the most widely used filler for plastics, caulks, sealants and coatings) , kaolin, talc, alumina trihydrate and organic fillers (e.g. ground byproducts and waste products based on wood, shells and rice.
  • Titanium dioxide is widely used as a white pigment, in paints and other compositions. However its use as a filler for adhesive compositions appears to be completely unknown. I have made extensive searches, e.g. of the websites of the main suppliers of Ti0 2 materials (ww . titanium, dupont .
  • the invention provides the use of a titanium dioxide (Ti0 2 ) material as a filler in an adhesive composition.
  • the adhesive composition generally comprises (a) a cross-linkable composition; and (b) a filler comprising titanium dioxide.
  • compositions of the invention employ synthetic adhesives such as hot melt, vinyl, rubber, urea, acrylic, polyethylene, epoxy and phenolic adhesives.
  • Phenolic adhesives are generally not preferred, as they tend to cure to highly coloured (usually deep red) products.
  • Preferred adhesives are those taught in W096/37551 (US 5880183) and US 3931088, which are incorporated herein by reference.
  • the cross-linkable composition may comprise one or more of the following components: (a) (i) a polymer containing units having hydroxy groups; (a) (ii) a polymer containing units having acetate • groups; (a) (iii) a polymer comprising styrene and/or butadiene and/or acrylonitrile derived units; (a) (iv) a cross-linker suitable for linking groups on one or more other components of the composition and/or on the substrate (e.g. hydroxy groups on a carbohydrate- containing substrate such as paper or wood) .
  • the cross-linkable composition may comprise urea resins, melamine-urea resins and phenol resin.
  • a component (a) (i) may comprise a solution of polyvinyl alcohol.
  • a component (a) (ii) may comprise a polyvinyl acetate homopolymer or copolymer, preferably an ethylene vinyl acetate copolymer or terpolymer.
  • A- component (a) (iii) may be a latex. It may comprise a polymer derived from an optionally substituted styrene monomer. It may contain units having carboxy units. It may be an SBR latex. It may comprise a latex of an acrylonitrile/butadiene copolymer.
  • a compound (a) (iv) may comprise a polyisocyanate or a polyfunctional aziridine (e.g.
  • the composition may be an aqueous composition comprising a polyvinyl alcohol and an isocyanate, e.g. as disclosed in US 3931088.
  • the composition may be a pre-catalysed polyvinyl acetate (PVAc) composition, e.g. containing A1C1 3 catalyst.
  • PVAc polyvinyl acetate
  • the invention provides an adhesive composition comprising (a) a cross-linkable composition and (b) a filler comprising titanium dioxide. Titanium dioxide may be the only filler. More usually it will be used together with one or more other fillers which may be conventional fillers, generally of much larger particle size (e.g.
  • titanium dioxide is a minor component of the total filler, e.g. 2-40% by weight, preferably 5-30%, more preferably 10-25%. Titanium dioxide may be used as a filler in adhesive compositions which are intrinsically colourless or light coloured, so that there would be no reason to use it as a pigment. ' Indeed, compositions such as those taught in W096/37551 and US 3931088 can be so pale (particularly when admixed with Ti0 2 ) that it is desirable to add pigments to darken and colour them so that they are less visible when used on wood. Of course different pigmentation may be appropriate for different woods.
  • the titanium dioxide preferably has particle sizes generally under 5 ⁇ m, preferably under 2 ⁇ m, and possibly even under O.l ⁇ , e.g. about 0.025 ⁇ m. Material with particle sizes ranging from 0.2 to 0.4 ⁇ m is widely available and generally suitable. (In comparison, materials conventionally used as fillers typically have particle sizes of 15-20 ⁇ m. )
  • the titanium dioxide preferably constitutes 10-50% by weight of the solid content of the composition and/or at least 5% of total filler weight. Use of titanium dioxide as a filler can offer one or more of the following advantages . i) The small particle size tends to give a small rate of sedimentation and hence a relatively long storage life. ii) The small particle size also leads to enhanced pot life or working life.
  • compositions can be of lower viscosity than corresponding compositions using only conventional fillers (due at least in part to particle size and/or smoothness) . This can enable (a) use of thinner layers of composition- and hence economy; (b) better and more rapid spreading and penetration into gaps and pores. This can enhance anchoring, which may be particularly valuable with hardwoods which tend to be of low porosity. It can be very useful in the production of veneers, especially thin veneers (e.g. 0.25mm thick) where it can be used for reinforcing veneers to reduce susceptibility to splitting and/or for lamination of veneers. iv) In a system also including larger particles (e.g.
  • Titanium dioxide is stable over a wide pH range (greater than pH3-10) .
  • adhesive compositions e.g. compositions containing ammonium chloride, like many urea-formaldehyde resins.
  • Calcium carbonate and clays tend not to be suitable for acidic compositions. Therefore flour is commonly used, but this is prone to sedimentation) .
  • the particles can be smoother than conventional filler particles (e.g. clays) . This can give lower water-absorbing capacity and hence faster setting.
  • the compositions containing titanium dioxide can easily be pigmented so as to match a particular substrate (e.g. wood type) . This is particularly useful for pale woods with exposed glue lines, and veneer laminates .
  • the particles of Ti0 2 are hard (6-7 mohs) . This leads to enhanced stiffness and strength of the set compositions and of substrates bonded with it. There are three crystalline forms of titanium dioxide: anatase, brookite and rutile. Rutile is preferred.
  • urea- formaldehyde (“UF”) resin is compounded with " a filler comprising titanium dioxide to uplift its bonding strength and setting speed and to reduce formaldehyde levels to achieve environmental compliance, e.g. for use for making bamboo composite flooring and some indoor materials.
  • a filler comprising titanium dioxide to uplift its bonding strength and setting speed and to reduce formaldehyde levels to achieve environmental compliance, e.g. for use for making bamboo composite flooring and some indoor materials.
  • Titanium dioxide is also suitable to mix into pre-catalyzed polyvinyl acetate (“PVAc”) to serve a similar purpose.
  • PVAc polyvinyl acetate
  • Pre-catalyzed PVAc dispersions containing A1C1 3 or other metal salts have been particularly problematic because their highly acidic nature (e.g. pH 3-4) prevents the use of conventional fillers. Thus it has not been possible using conventional fillers to achieve high solid contents.
  • a filler comprising Ti0 2
  • a filler comprising Ti0 2
  • Another type of embodiment employs an aqueous polymer isocyanate, as disclosed in US 3,931,088.
  • diphenyl methanediisocyanate (MDI) may be used with a butadiene latex.
  • Test 1 Glue Film Darkening of Aqueous Polymer Isocyanate Compositions
  • Carboxylated SBR latex (solid content : 50%) - 30 p.b.w.
  • Polyvinyl Alcohol Solution (s.c. 8%-9%) (BP-17, partially hydrolysii , from Chang Chung Taiwan) - 50 p.b.w.
  • Formulation B was prepared by homogeneously mixing 15% by weight of formula A into measured MDI - Lupranate M20S (supplied by BASF) . Surface portions (10 x 10 cm) of specimens of American hard maple wood were spread at a loading of 180g/m 2 . Sample API-1 received formulation A. Sample API-2 received formulation B. The samples were exposed to normal room conditions for 7 days.
  • API-1 white cloudy and very low opacity, wood grain clearly visible.
  • API-2 light amber colour, almost transparent, wood grain clearly visible.
  • Test 2 This was a repetition of Test 1, except that MDI was replaced by Suprasec / Rubinate 9236 (water emulsifiable) from Huntsman Polyurethane.
  • Test 3 This was a repetition of Test 1 using samples API3 and 4, except that the filler (25 pbw calcium carbonate in Test 1) was replaced by 20 pbw calcium carbonate and 5 pbw titanium dioxide.
  • Formulation A Formulation A
  • Formulation C same as Formulation A, but reversing the levels of SBR latex and PVAc.
  • Formulation D same as Formulation A except fillers are fully employed Ti0 2 .
  • Formulation E same as Formulation D, but reversing the levels of SBR latex and PVAc.
  • Test 5 Tests Complying with EN 204 Class D3 12 testpieces per test. 1.
  • Test 5-1 Formulation A-l Carboxylated Styrene butadiene rubber latex (solid content 50%) - 35 p.b.w. Polyvinyl acetate homopolymer dispersion (solid content 55%) - 41 p.b.w. Ground calcium carbonate powder (20 micron/1, 000 mesh) - 24 p.b.w. Sodium dodecyl benzene sulfonate (neutralized) - 0.2 p.b.w.
  • Stage 1 After 7 days in normal room conditions - 12.4 N/mm 2 Stage 2. 4 days of 23°C cold water soaking - 3.6 N/mm 2 Stage 3. 7 days room conditions after stage 2 - 8.3 N/mm 2
  • Test 5-2 Formulation A-2 Same as Formulation A-1 but fillers varied to ground calcium carbonate (20 pbw) & Ti0 2 (4 pbw) . Results : Average Lap Shear Strength.
  • Specimens 2 pieces of American hard maple, surface measurement 6 x 6 cm.
  • Test 5-4 Setting Speeds Formulations A-1 and A-2 were used as in test 5-1. They were used for bonding a maple wood veneer to medium density fibre board (MDF) .
  • the samples of veneer and MDF were of surface area 50x50cm.
  • the veneer was of thickness 0.8mm (approximately).
  • the MDF board was of thickness 15mm (approximately) .
  • Formulations A-1 and A-2 were applied to respective samples of the MDF board at approximately 180g/m 2 . Immediately, samples of the veneers were laminated onto the MDF boards, and the laminates were pressed in a hot press for 20 seconds at 112°C. They were then swiftly removed from the hot press.
  • an adhesive formulation . embodying the present invention may be set under milder conditions (e.g. lower temperature 10 and/or lower heating time) means that its loss of water may be reduced, and the tendency to warp may thus be reduced.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Inorganic Chemistry (AREA)
  • Adhesives Or Adhesive Processes (AREA)

Abstract

The use of Ti02 as a filler in an adhesive composition gives many advantages, mainly due to the small particle size, e.g. 0.2-0.4µm. Advantages include long storage life and pot life and low viscosity. It can also be used at extreme pHs, e.g. in acid compositions (e.g. containing AlCl3) or in contact with alkaline cement. The adhesive compositions may comprise one or more of PVAc, PVOH, styrene-butadiene latex and crosslinkers such as polyisocyanates and polyaziridines.

Description

ADHESIVE COMPOSITION
The present invention relates to an adhesive composition, to the preparation of the composition, to uses of the composition, and to products of such use. It is particularly but not . exclusively concerned with adhesive compositions for wood and wood-based materials . Exemplary compositions include wood glues, wood sealers, putties, wood surface reinforcing agents, and impregnants for paper or card. The present compositions find particular, but not exclusive, use as adhesives and binding, coating and sealing materials. They may be used in producing ^modified woods' . In another aspect the invention provides a new use for titanium dioxide (Ti02) . Many adhesives currently available, particularly for use in woodworking, contain polyvinyl alcohol (PVOH) or a dispersion of another polymer such as polyvinyl acetate (PVAc) in polyvinyl alcohol (PVOH) . The adhesives operate by forming a physical bond with the wood substrate. In this respect the -OH groups in the adhesive composition and the -_OH groups from cellulose in the wood substrate together form strong hydrogen bonds. WO 96/37551 and US 5880183 (YEO) disclose adhesives in the form of a pack containing components A and B. Component A contains: (Ai) a solution or dispersion comprising a polymer containing units having hydroxyl groups, and (Aii) a polymer derived from an optionally substituted styrene monomer, said polymer containing units having carboxyl groups. Component B comprises (Bi) a polyfunctional aziridine crosslinker capable of crosslinking with at least one carboxyl group and at least one hydroxyl group. Preferably the component A includes polymers containing acetate groups, e.g. polyvinyl acetate homopolymers or copolymers, (e.g. an ethylene vinyl acetate copolymer or terpolymer) , preferably as a dispersion with polyvinyl alcohol. The composition may contain a filler, for improving water resistance. Talc, silica, kaolin and calcium carbonate are exemplified. US-A-3,931,088 (assigned to Kuraray Co., Ltd.) discloses an adhesive composition comprising (1) an aqueous solution of polyvinyl alcohol and (2) a hydrophobic solution of a polyisocyanate compound. Preferred further ingredients include an aqueous emulsion of vinyl acetate polymer and/or an aqueous latex of butadiene polymer such as an aqueous latex of a copolymer of styrene and butadiene or an aqueous latex of a copolymer of acrylonitrile and butadiene. It states that urea resins, melamine-urea co-condensation resins and phenol resins are predominately used as the adhesives for making plywood. These adhesives are widely used because of their low price and relatively good water-resistance; however it had been found that such adhesives tend to release formaldehyde, so alternatives were desired. It is disclosed that fillers may be used: "suitable fillers include organic substances such as wood powder and powder of walnut shell, etc., as well as inorganic substances, such as clay, kaolin and talc, etc." The effect of the filler is stated to be: "not only to prevent excessive penetration of adhesive into the wood, but also to impart better water resistance and initial adhesive strength by reacting with the isocyanate". The article on "Fillers" in "Concise Encyclopaedia of Polymer Science and Engineering", ed. J. I. Kroschwitz, USA, 1990, states that "Fillers include calcium carbonate (the most widely used filler for plastics, caulks, sealants and coatings) , kaolin, talc, alumina trihydrate and organic fillers (e.g. ground byproducts and waste products based on wood, shells and rice. " Titanium dioxide is widely used as a white pigment, in paints and other compositions. However its use as a filler for adhesive compositions appears to be completely unknown. I have made extensive searches, e.g. of the websites of the main suppliers of Ti02 materials (ww . titanium, dupont . com, -and www, huntsman, com) and textbooks (e.g. the Concise Encyclopaedia referred to above) without finding any references to such uses. This may be at least partly due to the cost of Ti02 materials: about 10 times that of the usual clay-type fillers. However I have now discovered that the use of titanium dioxide as a filler in adhesive compositions can give substantial and unexpected advantages . Thus in a first aspect the invention provides the use of a titanium dioxide (Ti02) material as a filler in an adhesive composition. The adhesive composition generally comprises (a) a cross-linkable composition; and (b) a filler comprising titanium dioxide. Generally the compositions of the invention employ synthetic adhesives such as hot melt, vinyl, rubber, urea, acrylic, polyethylene, epoxy and phenolic adhesives. Phenolic adhesives (including resorcinolic adhesives) are generally not preferred, as they tend to cure to highly coloured (usually deep red) products. Preferred adhesives are those taught in W096/37551 (US 5880183) and US 3931088, which are incorporated herein by reference. The cross-linkable composition may comprise one or more of the following components: (a) (i) a polymer containing units having hydroxy groups; (a) (ii) a polymer containing units having acetate • groups; (a) (iii) a polymer comprising styrene and/or butadiene and/or acrylonitrile derived units; (a) (iv) a cross-linker suitable for linking groups on one or more other components of the composition and/or on the substrate (e.g. hydroxy groups on a carbohydrate- containing substrate such as paper or wood) . The cross-linkable composition may comprise urea resins, melamine-urea resins and phenol resin. • A component (a) (i) may comprise a solution of polyvinyl alcohol. A component (a) (ii) may comprise a polyvinyl acetate homopolymer or copolymer, preferably an ethylene vinyl acetate copolymer or terpolymer. A- component (a) (iii) may be a latex. It may comprise a polymer derived from an optionally substituted styrene monomer. It may contain units having carboxy units. It may be an SBR latex. It may comprise a latex of an acrylonitrile/butadiene copolymer. A compound (a) (iv) may comprise a polyisocyanate or a polyfunctional aziridine (e.g. as disclosed in WO 96/37551) . This will generally be provided in a separate part of a two-part pack. The composition may be an aqueous composition comprising a polyvinyl alcohol and an isocyanate, e.g. as disclosed in US 3931088. The composition may be a pre-catalysed polyvinyl acetate (PVAc) composition, e.g. containing A1C13 catalyst. In another aspect the invention provides an adhesive composition comprising (a) a cross-linkable composition and (b) a filler comprising titanium dioxide. Titanium dioxide may be the only filler. More usually it will be used together with one or more other fillers which may be conventional fillers, generally of much larger particle size (e.g. kaolin, calcium carbonate) . Usually titanium dioxide is a minor component of the total filler, e.g. 2-40% by weight, preferably 5-30%, more preferably 10-25%. Titanium dioxide may be used as a filler in adhesive compositions which are intrinsically colourless or light coloured, so that there would be no reason to use it as a pigment.' Indeed, compositions such as those taught in W096/37551 and US 3931088 can be so pale (particularly when admixed with Ti02) that it is desirable to add pigments to darken and colour them so that they are less visible when used on wood. Of course different pigmentation may be appropriate for different woods. The titanium dioxide preferably has particle sizes generally under 5μm, preferably under 2μm, and possibly even under O.lμ, e.g. about 0.025μm. Material with particle sizes ranging from 0.2 to 0.4μm is widely available and generally suitable. (In comparison, materials conventionally used as fillers typically have particle sizes of 15-20μm. ) The titanium dioxide preferably constitutes 10-50% by weight of the solid content of the composition and/or at least 5% of total filler weight. Use of titanium dioxide as a filler can offer one or more of the following advantages . i) The small particle size tends to give a small rate of sedimentation and hence a relatively long storage life. ii) The small particle size also leads to enhanced pot life or working life. iii) Compositions can be of lower viscosity than corresponding compositions using only conventional fillers (due at least in part to particle size and/or smoothness) . This can enable (a) use of thinner layers of composition- and hence economy; (b) better and more rapid spreading and penetration into gaps and pores. This can enhance anchoring, which may be particularly valuable with hardwoods which tend to be of low porosity. It can be very useful in the production of veneers, especially thin veneers (e.g. 0.25mm thick) where it can be used for reinforcing veneers to reduce susceptibility to splitting and/or for lamination of veneers. iv) In a system also including larger particles (e.g. of conventional filler such as clay, and/or of polymer) , the small particles can occupy interstices between the larger particles, leading to a reduction in capillary size. This can improve properties of the crosslinked product, e.g. stiffness, strength, and water and- heat resistance. v) Titanium dioxide is stable over a wide pH range (greater than pH3-10) . Thus it is compatible with many adhesive compositions, e.g. compositions containing ammonium chloride, like many urea-formaldehyde resins. (Calcium carbonate and clays tend not to be suitable for acidic compositions. Therefore flour is commonly used, but this is prone to sedimentation) . It can be used in producing plywood coatings for concrete moulding panels, where resistance to cement alkalinity is desirable. vi) The particles can be smoother than conventional filler particles (e.g. clays) . This can give lower water-absorbing capacity and hence faster setting. vii) The compositions containing titanium dioxide can easily be pigmented so as to match a particular substrate (e.g. wood type) . This is particularly useful for pale woods with exposed glue lines, and veneer laminates . viii) The particles of Ti02 are hard (6-7 mohs) . This leads to enhanced stiffness and strength of the set compositions and of substrates bonded with it. There are three crystalline forms of titanium dioxide: anatase, brookite and rutile. Rutile is preferred. Anatase may be used. In one preferred type of embodiment, urea- formaldehyde ("UF") resin is compounded with" a filler comprising titanium dioxide to uplift its bonding strength and setting speed and to reduce formaldehyde levels to achieve environmental compliance, e.g. for use for making bamboo composite flooring and some indoor materials. Titanium dioxide is also suitable to mix into pre-catalyzed polyvinyl acetate ("PVAc") to serve a similar purpose. Pre-catalyzed PVAc dispersions containing A1C13 or other metal salts have been particularly problematic because their highly acidic nature (e.g. pH 3-4) prevents the use of conventional fillers. Thus it has not been possible using conventional fillers to achieve high solid contents. By using a filler comprising Ti02, one can easily reach solid contents of 60% or more. This can give advantageous properties such as water and heat resistance, stiffness, gap-filling ability, and faster setting. Another type of embodiment employs an aqueous polymer isocyanate, as disclosed in US 3,931,088. For example, diphenyl methanediisocyanate (MDI) may be used with a butadiene latex. Some embodiments of the inventions and comparative examples will now be described.
Test 1: Glue Film Darkening of Aqueous Polymer Isocyanate Compositions
Formulation A was prepared with the following composition and characteristics:
Formulation A:
Carboxylated SBR latex (solid content : 50%) - 30 p.b.w.
Polyvinyl Acetate Dispersion (s.c. 55%) - 20 p.b.w.
Polyvinyl Alcohol Solution (s.c. 8%-9%) (BP-17, partially hydrolysii , from Chang Chung Taiwan) - 50 p.b.w.
Ground Calcium Carbonate (particle size : 20 microns) - 25 p.b.w.
Sodium dodecyl benzene sulfonate (s.c. 50%) - 0.3 p.b.w.
Solid content : approx 44%. Viscosity : 2,500 cps. pH : approx. 7.5.
Formulation B was prepared by homogeneously mixing 15% by weight of formula A into measured MDI - Lupranate M20S (supplied by BASF) . Surface portions (10 x 10 cm) of specimens of American hard maple wood were spread at a loading of 180g/m2. Sample API-1 received formulation A. Sample API-2 received formulation B. The samples were exposed to normal room conditions for 7 days.
Glue film results:
API-1 - white cloudy and very low opacity, wood grain clearly visible. API-2 - light amber colour, almost transparent, wood grain clearly visible. Test 2 This was a repetition of Test 1, except that MDI was replaced by Suprasec / Rubinate 9236 (water emulsifiable) from Huntsman Polyurethane.
Results: Same as Test 1.
Test 3 This was a repetition of Test 1 using samples API3 and 4, except that the filler (25 pbw calcium carbonate in Test 1) was replaced by 20 pbw calcium carbonate and 5 pbw titanium dioxide.
After 7 days, the glue films were fully opaque ivory white, and the wood grain was entirely invisible.
The presence of Ti02 led to faster setting speed, and the cured glue films were more Λstiff-tough' than corresponding films of Test 1.
Conclusion: Ti02 is able to elevate film strength, and also provide pigmentable environment for desired wood colours to reduce glue line visibility. Test 4 : Sedimentation
Specimens :
(I) Formulation A (II) Formulation C - same as Formulation A, but reversing the levels of SBR latex and PVAc. (III) Formulation D - same as Formulation A except fillers are fully employed Ti02. (IV) Formulation E - same as Formulation D, but reversing the levels of SBR latex and PVAc.
Testing Detail All specimens placed in normal room conditions for 2 weeks.
Results: Specimen (I) - Slight sedimentation found. Specimen (II) - Much more than specimen (I) . Specimen (III) & (IV) - No sedimentation found.
Test 5: Tests Complying with EN 204 Class D3 12 testpieces per test. 1. Test 5-1 - Formulation A-l Carboxylated Styrene butadiene rubber latex (solid content 50%) - 35 p.b.w. Polyvinyl acetate homopolymer dispersion (solid content 55%) - 41 p.b.w. Ground calcium carbonate powder (20 micron/1, 000 mesh) - 24 p.b.w. Sodium dodecyl benzene sulfonate (neutralized) - 0.2 p.b.w.
Add Polyfunctional Aziridine crosslinker (CX-100 from Avecia) - 3 p.b.w.
Results : Average Lap Shear Strength.
Stage 1. After 7 days in normal room conditions - 12.4 N/mm2 Stage 2. 4 days of 23°C cold water soaking - 3.6 N/mm2 Stage 3. 7 days room conditions after stage 2 - 8.3 N/mm2
2. Test 5-2 - Formulation A-2 Same as Formulation A-1 but fillers varied to ground calcium carbonate (20 pbw) & Ti02 (4 pbw) . Results : Average Lap Shear Strength.
Stage 1. 13.6 N/mm2 Stage 2. 4.2 N/mm2 Stage 3. 8.8 N/mm2
Setting speed and stiffness-toughness greater than for A-1 (withou Ti02) .
Test 5-3
Specimens : 2 pieces of American hard maple, surface measurement 6 x 6 cm.
Testing Details (a) Specimen 3-3-1 coated with Formulation A-1 (crosslinked) . (b) Specimen 3-3-2 coated with Formulation A-2 (crosslinked) .
7 days normal conditions and placed under direct sunlight for 6 hours/day consecutive for 7 days.
(a) Specimen 3-3-1 cloudy translucent off-white colour and light translucent amber colour after sunlight exposure. (b) Specimen 3-3-2 white opaque colour even after sunlight exposure. No visible colour change.
Conclusion: Enhanced bonding strength and water resistance with the participation of Ti0. Consistent colour before and after light exposure. Glue film becomes pigmentable to desired colour, e.g. to match darker woods like rosewood and ebony to suppress visible glue lines.
4. Test 5-4: Setting Speeds Formulations A-1 and A-2 were used as in test 5-1. They were used for bonding a maple wood veneer to medium density fibre board (MDF) . The samples of veneer and MDF were of surface area 50x50cm. The veneer was of thickness 0.8mm (approximately). The MDF board was of thickness 15mm (approximately) .
(1) Formulations A-1 and A-2 were applied to respective samples of the MDF board at approximately 180g/m2. Immediately, samples of the veneers were laminated onto the MDF boards, and the laminates were pressed in a hot press for 20 seconds at 112°C. They were then swiftly removed from the hot press.
Result: Both adhesives (A-1 and A-2) were fully set, and both veneers were successfully laminated on the MDF board.
(2) The procedure was repeated, except that the hot pressing time was reduced to 15 seconds. Once again the formulation A-2 (including titanium dioxide) was fully set. It was difficult to separate the veneer from the MDF. When they were forced apart, there was obvious fibre tear. However, the laminate employing formulation A-1 (without titanium dioxide) was not fully set. It was possible to lift up the veneer with little evidence of fibre tear. Thus the inclusion of Ti02 in the formulation led to faster setting speed. This could be used for substantial increase in productivity. The easier setting of formulations embodying the invention can have other advantages too. Wood and other natural-type and related materials (e.g. paper) tend to have a water content. This may be in equilibrium with atmospheric moisture. If the water content is reduced (e.g. by heating), and the 5 material is subsequently returned to normal atmospheric conditions, it may tend to warp. The fact that an adhesive formulation . embodying the present invention may be set under milder conditions (e.g. lower temperature 10 and/or lower heating time) means that its loss of water may be reduced, and the tendency to warp may thus be reduced.

Claims

CLAIMS :
1. An adhesive composition comprising (a) a synthetic adhesive selected from hot melt, vinyl, rubber, urea, acrylic, polyethylene and epoxy adhesives; and (b) a filler comprising titanium dioxide.
2. An adhesive composition according to claim 1 wherein the adhesive (a) comprises one or more of the • following components: (a) (i) a polymer containing units having hydroxy groups; (a) (ii) a polymer containing units having acetate groups; (a) (iii) a polymer comprising styrene and/or butadiene and/or acrylonitrile derived units; (a) (iv) a cross-linker suitable for linking groups on one or more other components of the composition and/or on the substrate.
3. An adhesive composition according to claim 2 including a component (a) (i) comprising a solution of polyvinyl alcohol .
4. An adhesive composition according to claim 2 or 3 including a component (a) (ii) comprising a polyvinyl acetate homopolymer or copolymer.
5. An adhesive composition according to claim 2, 3 or 4 including a component (a) (ii) which comprises an ethylene vinyl acetate copolymer or terpolymer.
6. An adhesive composition according to claim 2, 3, 4 or 5 including a component (a) (iii) comprising a polymer derived from an optionally substituted styrene monomer.
7. An adhesive composition according to any of claims 2-6 including a compound (a) (iv) comprising a polyisocyanate or a polyfunctional aziridineT
8. An adhesive composition according to any preceding claim wherein the adhesive comprises one or more of urea resins and melamine-urea resins.
9. An adhesive composition according to any preceding claim wherein the titanium dioxide has particle sizes generally under 5μm
10. An adhesive composition according to any preceding claim wherein the titanium dioxide has particle sizes generally under 2μm.
11. An adhesive composition according to any preceding claim wherein, the titanium dioxide constitutes 10-50% by weight of the solid content of the composition and/or at least 5% of total filler weight.
12. An adhesive composition according to any preceding claim which includes a pigment for darkening the colour of the composition.
13. Use of titanium dioxide as a filler in an adhesive composition.
14. Use according to claim 13 wherein the adhesive composition is according to any of claim 1-12.
15. A substrate to which an adhesive composition according to any of claims 1-12 has been applied.
PCT/SG2004/000059 2004-03-18 2004-03-18 Adhesive composition WO2005087889A1 (en)

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DE102005018728A1 (en) * 2005-04-22 2006-11-09 Heinrich Hahne Gmbh & Co. Kg Sealing mass, useful for buildings, preferably balconies, comprises a component of an aqueous plastic dispersion of carboxylated butadiene styrol copolymer and a component of hydrophilic and aliphatic polyisocyanate
WO2009033672A1 (en) * 2007-09-11 2009-03-19 Quadrant Plastic Composites Ag Composite sheet based on high pressure laminate sheets (hpl sheets)
DE102009006936A1 (en) * 2009-01-30 2010-08-05 Tesa Se Release agent, in particular for an adhesive tape
JP2014522426A (en) * 2011-05-16 2014-09-04 アシュランド・インコーポレーテッド Two-component polyurea-urethane adhesive with high high temperature storage modulus
JP2015166429A (en) * 2014-03-04 2015-09-24 アイカ工業株式会社 Water-based adhesive
JP2016166293A (en) * 2015-03-10 2016-09-15 アイカ工業株式会社 Water-based adhesive
CN107779124A (en) * 2017-11-02 2018-03-09 新辉（中国）新材料有限公司 A kind of method for preparing modified butadiene-styrene latex, thus obtained modified butadiene-styrene latex and its application
CN107964380A (en) * 2017-12-28 2018-04-27 石家庄惠得科技有限公司 A kind of Non-Gaussian Distribution aluminium hydrate powder and its preparation method and application

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Publication number Priority date Publication date Assignee Title
DE102005018728A1 (en) * 2005-04-22 2006-11-09 Heinrich Hahne Gmbh & Co. Kg Sealing mass, useful for buildings, preferably balconies, comprises a component of an aqueous plastic dispersion of carboxylated butadiene styrol copolymer and a component of hydrophilic and aliphatic polyisocyanate
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WO2009033672A1 (en) * 2007-09-11 2009-03-19 Quadrant Plastic Composites Ag Composite sheet based on high pressure laminate sheets (hpl sheets)
DE102009006936A1 (en) * 2009-01-30 2010-08-05 Tesa Se Release agent, in particular for an adhesive tape
JP2014522426A (en) * 2011-05-16 2014-09-04 アシュランド・インコーポレーテッド Two-component polyurea-urethane adhesive with high high temperature storage modulus
JP2015166429A (en) * 2014-03-04 2015-09-24 アイカ工業株式会社 Water-based adhesive
JP2016166293A (en) * 2015-03-10 2016-09-15 アイカ工業株式会社 Water-based adhesive
CN107779124A (en) * 2017-11-02 2018-03-09 新辉（中国）新材料有限公司 A kind of method for preparing modified butadiene-styrene latex, thus obtained modified butadiene-styrene latex and its application
CN107964380A (en) * 2017-12-28 2018-04-27 石家庄惠得科技有限公司 A kind of Non-Gaussian Distribution aluminium hydrate powder and its preparation method and application
CN107964380B (en) * 2017-12-28 2020-05-12 石家庄惠得科技有限公司 Non-normal distribution aluminum hydroxide powder and preparation method and application thereof

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