Adhesive composition

Abstract

The present disclosure generally provides adhesive compositions, and more particularly, provides a polyfunctional isocyanate adhesive composition that can be used in the preparation of composite wood boards, wherein the adhesive composition comprises (a) a polyfunctional isocyanate or an isocyanate prepolymer, wherein the isocyanate prepolymer is obtained by reacting a polyfunctional isocyanate with a polyfunctional polyol; (b) a tackifier; and (c) a phosphate ester. The composition has high tack and improved demolding ability.

Description

Technical Field

[0001] The present disclosure relates generally to adhesive compositions, and more particularly to multifunctional isocyanate adhesive compositions useful in preparing composite wood panels. Background Art

[0002] The use of isocyanate, tackifier, and release agent mixtures to form lignocellulosic composites is known in the art.

[0003] WO2009061474 discloses an adhesive comprising a blend of isocyanate, tackifier and release agent, but the type and amount of release agent used in this patent application are different from those disclosed herein.

[0004] WO20150484441 discloses a diisocyanate, a tackifier, and a phosphate blend adhesive. However, the amount of phosphate ester and the type of tackifier used in that patent application are different from those of the present disclosure.

[0005] However, known solutions do not provide adhesive compositions with high tack capabilities and improved demoulding capabilities that can be applied to composite wood boards. Summary of the Invention

[0006] It has now been surprisingly discovered that the compositions and methods of the present disclosure solve the above problems. Advantages of the present disclosure may include: (1) high tack ability; (2) improved demoulding ability; and (3) environmental friendliness.

[0007] The present disclosure relates to adhesive compositions and methods of making these compositions. In one embodiment, the present disclosure provides an adhesive composition comprising: (a) a polyfunctional isocyanate or an isocyanate prepolymer, wherein the isocyanate prepolymer is obtained by reacting a polyfunctional isocyanate with a polyfunctional polyol; (b) a tackifier; and (c) a phosphate ester.

[0008] In another embodiment, the present disclosure provides a method for preparing an adhesive composition.

[0009] In yet another embodiment, the present disclosure provides methods of using the adhesive composition in the preparation of composite wood panels, preferably particleboard and plywood. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a graph depicting the effect of time on viscosity level for the formulations of Examples 1 to 8.

[0011] Figure 2A shows a particleboard test using the composition of Example 9 in a pre-compression step, wherein a release agent of the present disclosure is used; Figure 2BShown are particleboard tests using the composition of Example 10 in a pre-compression step, wherein a release agent not according to the present disclosure is used; Figure 2C Particleboard tests using the composition of Example 11 in a pre-compression step are shown, wherein no release agent was used. DETAILED DESCRIPTION

[0012] If it appears in this document, the term "comprising" and its derivatives are not intended to exclude the presence of any additional components, steps or procedures, whether or not they are disclosed herein. For the avoidance of any doubt, all compositions claimed herein through the use of the term "comprising" may include any additional additives, adjuvants or compounds unless otherwise stated. In contrast, the term "consisting essentially of, if it appears in this document, excludes the scope of any subsequent recitation of any other components, steps or procedures, except those that are not essential to operability, and the term "consisting of, if used, excludes any components, steps or procedures that are not specifically described or listed. Unless otherwise stated, the term "or" refers to the listed members individually and in any combination.

[0013] The articles "a" and "an" are used herein to refer to one or more than one / a kind or more than one (ie, at least one / at least one) of the grammatical object of the article. For example, "a resin" means one resin or more than one resin.

[0014] The phrases "in one embodiment," "according to one embodiment," etc. generally mean that the particular feature, structure, or characteristic following the phrase is included in at least one embodiment of the present invention, and may be included in more than one embodiment of the present invention. Importantly, these phrases are not necessarily referring to the same embodiment.

[0015] If the specification states that a component or feature "may," "could," "would," or "might" be included or have a property, that particular component or feature is not required to be included or have that property.

[0016] The present disclosure generally provides an adhesive composition comprising: (a) a polyfunctional isocyanate or an isocyanate prepolymer, wherein the isocyanate prepolymer is obtained by reacting a polyfunctional isocyanate with a polyfunctional polyol; (b) a tackifier; and (c) a phosphate ester.

[0017] According to one embodiment, the polyfunctional isocyanate comprises a compound of formula Q(NCO) n Those represented by wherein n is a number of 2 to 5, preferably 2 to 3, and Q is an aliphatic hydrocarbon group containing 2 to 18 carbon atoms, an alicyclic hydrocarbon group containing 5 to 10 carbon atoms, an aromatic aliphatic hydrocarbon group containing 8 to 13 carbon atoms, or an aromatic hydrocarbon group containing 6 to 15 carbon atoms, wherein aromatic hydrocarbon groups are generally preferred.

[0018] Examples of polyfunctional isocyanates include, but are not limited to, ethylene diisocyanate; 1,4-tetramethylene diisocyanate; 1,6-hexamethylene diisocyanate; 1,12-dodecane diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-1,3- and -1,4-diisocyanates, and mixtures of these isomers; isophorone diisocyanate; 2,4- and 2,6-hexahydrotoluene diisocyanate and mixtures of these isomers; dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI or HMDI); 1,3- and 1,4-phenylene diisocyanate; 2,4- and 2,6-toluene diisocyanate and mixtures of these isomers (TDI); diphenylmethane-2,4'-diisocyanate; - and / or -4,4'-diisocyanate (MDI); naphthylene-1,5-diisocyanate; triphenylmethane-4,4',4''-triisocyanate; polyphenylpolymethylene polyisocyanates of the type obtainable by condensation of aniline with formaldehyde followed by phosgenation (polymeric MDI); norbornane diisocyanate; m- and p-isocyanatophenylsulfonyl isocyanates; perchloroaryl polyisocyanates; modified polyfunctional isocyanates containing carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups; polyfunctional isocyanates obtained by telomerization; polyfunctional isocyanates containing ester groups; and polyfunctional isocyanates containing polymeric fatty acid groups. Those skilled in the art will recognize that mixtures of the aforementioned polyfunctional isocyanates can also be used, preferably mixtures of polymeric MDI, mixtures of MDI isomers and mixtures of TDI.

[0019] In another embodiment, prepolymers of MDI or TDI can also be used as substitutes for MDI or TDI. Prepolymers of MDI or TDI are prepared by reacting an excess of the above-mentioned polyfunctional isocyanates (such as MDI or TDI) with a polyfunctional polyol. The prepolymers preferably have an NCO value of 20-35% by weight. Methods for synthesizing prepolymers of MDI or TDI are known in the art (see, for example, the Polyurethanes Handbook, 2nd edition, G. Oertel, 1994).

[0020] The polyfunctional polyols used in the present disclosure may include, but are not limited to, polyether polyols, polyester polyols, biorenewable polyols, polymer polyols, non-flammable polyols such as phosphorus-containing polyols or halogen-containing polyols. Such polyols may be used alone or in a suitable combination in the form of a mixture.

[0021] The multifunctional polyols used in the present invention typically have a functionality of 2 to 6.

[0022] Polyether polyols useful in the present disclosure include alkylene oxide polyether polyols, such as ethylene oxide polyether polyols and propylene oxide polyether polyols, and copolymers of ethylene oxide and propylene oxide having terminal hydroxyl groups derived from polyols, including diols and triols; for example, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, pentaerythritol, glycerol, diglycerol, trimethylolpropane, and similar low molecular weight polyols.

[0023] The polyester polyols used in the present invention include, but are not limited to, those prepared by reacting a dicarboxylic acid with an excess of a diol, such as adipic acid with ethylene glycol or butanediol, or a lactone with an excess of a diol, such as caprolactone with propylene glycol. In addition, the polyester polyols used in the present invention may also include: linear or slightly branched aliphatic (mainly adipate) polyols with terminal hydroxyl groups; low molecular weight aromatic polyesters; polycaprolactone; polycarbonate polyols. These linear or slightly branched aliphatic (mainly adipate) polyols with terminal hydroxyl groups are prepared by reacting a dicarboxylic acid with an excess of a diol, a triol, and a mixture thereof; these dicarboxylic acids include, but are not limited to, for example, adipic acid and AGS mixed acid; these diols and triols include, but are not limited to, for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, and pentaerythritol. These low molecular weight aromatic polyesters include products derived from process residues from dimethyl terephthalate (DMT) production (commonly referred to as DMT still bottoms), products derived from the fermentation of recycled polyethylene terephthalate (PET) bottles or tapes and subsequent re-esterification with diacids or reaction with alkylene oxides, and products derived by the targeted esterification of phthalic anhydride. Polycaprolactones are prepared by ring-opening caprolactone in the presence of an initiator and a catalyst. Initiators include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, and pentaerythritol. Polycarbonate polyols are derived from carbonic acid and can be produced by polycondensation of a diol with phosgene, by transesterification of a diol (usually hexanediol) with a carbonate (e.g., diphenyl carbonate).

[0024] Biorenewable polyols suitable for use in the present invention include castor oil, sunflower oil, palm kernel oil, palm oil, canola oil, rapeseed oil, soybean oil, corn oil, peanut oil, olive oil, algae oil, and mixtures thereof.

[0025] Examples of polyfunctional polyols also include, but are not limited to, graft polyols or polyurea-modified polyols. Graft polyols include triols in which vinyl monomers are graft copolymerized. Suitable vinyl monomers include, for example, styrene or acrylonitrile. Polyurea-modified polyols are polyols containing a polyurea dispersion formed by the reaction of a diamine and a diisocyanate in the presence of a polyol. A variant of polyurea-modified polyols is a polyisocyanate polyaddition (PIPA) polyol, which is formed by the in-situ reaction of an isocyanate and an alkanolamine in a polyol.

[0026] The non-flammable polyol may be, for example, a phosphorus-containing polyol obtainable by adding an alkylene oxide to a phosphoric acid compound. The halogen-containing polyol may be, for example, one obtainable by ring-opening polymerization of epichlorohydrin or trichlorobutylene oxide.

[0027] In a preferred embodiment, the polyfunctional polyol is a polyether polyol.

[0028] Suitable tackifiers for use in the present disclosure may include homopolymers of vinyl acetate or copolymers of vinyl acetate or mixtures thereof.

[0029] In a preferred embodiment, the tackifier is a copolymer of vinyl acetate, more preferably a vinyl acetate-ethylene copolymer.

[0030] The molecular weight of the tackifier may range from 10,000 to about 2,000,000, preferably from 100,000 to about 1,000,000.

[0031] Molecular weight (MW) is the weight average molecular weight as determined by gel permeation chromatography (GPC) using polystyrene as a reference.

[0032] The proportion of the tackifier is generally in the range from 0.5% to 80% by weight, preferably from 5% to 50%, based on the adhesive composition.

[0033] A release agent is a chemical used to prevent other materials from bonding to a surface. It provides a critical barrier between the molding surface and the substrate, facilitating separation of the cured part from the mold. Without this barrier in place, the substrate will become fused to the mold surface, leading to difficult cleanup and a significant loss in production efficiency. Even when a release agent is used, improper selection can have a significant impact on the quality and consistency of the finished product.

[0034] It was discovered that the addition of phosphate esters to the adhesive composition of the present disclosure can improve mold release capabilities.

[0035] In a preferred embodiment, the phosphate ester is an alkyl ether phosphate ester or a mixture of an alkyl phosphate ester and an alkyl ether phosphate ester.

[0036] The molecular weight of the phosphate ester may range from about 200 to about 2,000, preferably from about 300 to about 1,000.

[0037] The weight ratio of the tackifier to the phosphate ester is in the range of about 30:1 to about 20,000:1, preferably about 500:1 to about 2,000:1.

[0038] In the present disclosure, the composition further comprises a wax.

[0039] In one embodiment, the proportion of the wax present in the adhesive composition is in the range of 1.5% to 50% by weight, preferably 15% to 30%, based on the total weight of the adhesive composition.

[0040] In another embodiment, the adhesive composition may further optionally comprise a flame retardant, an antioxidant, a solvent, a surfactant, a cross-linking agent, a filler, a pigment, or any other typical additive used in isocyanate materials.

[0041] Advantages of the disclosed compositions may include: (1) high tack ability; (2) improved mold release ability; and (3) environmental friendliness.

[0042] The present disclosure also provides a method for preparing an adhesive composition, the method comprising mixing a tackifier and a phosphate ester in a first step, and then adding a multifunctional isocyanate or an isocyanate prepolymer in a second step.

[0043] Additionally, the present disclosure provides methods of using the adhesive composition in the preparation of composite wood panels, preferably particleboard and plywood.

[0044] The following embodiments should now be considered as illustrative of the present disclosure and not limiting of the present disclosure in any way.

[0045] raw materials

[0046] Multifunctional isocyanate: SUPRASEC® 5005 polymeric MDI (supplier: Huntsman Corporation, USA);

[0047] Isocyanate prepolymer: I-BOND® PB EFC 4322 MDI prepolymer (supplier: Huntsman Corporation, USA);

[0048] Tackifier A: EAF 7012 vinyl acetate copolymer (supplier: Wacker Chemicals, Nanjing, China);

[0049] Tackifier B: 1502 polymerized styrene butadiene rubber (supplier: Sinopec Qilu Petrochemical, China);

[0050] Tackifier C: PU-608 polyurethane dispersion (supplier: Guangzhou Guanzhi New Material Technology, China);

[0051] UF: UFC80 urea-formaldehyde resin (supplier: Dynea Guangdong, China);

[0052] Release agent A: Tech Lube HB-550D alkyl ether phosphate (supplier: Technick Products, USA);

[0053] Release agent B: 1310P trideceth-10 phosphate (supplier: Nantong Chenrun Chemical, China);

[0054] Release agent C: FR-1000A fluorinated silicone (supplier: Neos Shanghai, China);

[0055] Wax: FR54 fully refined paraffin wax (supplier: PetroChina Chemical Industry Company Limited, China).

[0056] Examples 1-8:

[0057] The components of the adhesive compositions of Examples 1 to 8 are shown in Table 1. All values ​​listed in Table 1 refer to parts by weight of the components. As shown in Table 1, Example 7 is a blank example containing no tackifier or phosphate ester. Example 8 is a comparative example containing UF as the adhesive.

[0058] Table 1

[0059]

[0060] program

[0061] For each of Examples 1-8, wood shavings (B) are blended for about 60 seconds in a small food processor, while each component of adhesive composition (A) is added drop-wise to the wood shavings one by one, while mixing in the ratio (by weight) of A:B=1:20, and water is added to the blended material to control the water content of the blended material to 30%. After mixing, the blended material is removed from the food processor and placed in the hands of the experimenter (holding hand). In the next step, an attempt is made in the hand by compressing the material for three seconds to make a ball. Compression is completed by squeezing the ball with the holding hand. The viscosity rating of the ball is then given based on the integrity of the formed ball. The rating system is shown in Table 2 below. After the viscosity assessment, a new ball is made, then placed on the top of the laboratory workbench in the form of a neat pile, and viscosity is tested again every 5 minutes, until 40 minutes have passed from the blending time. Viscosity assessment is carried out according to methods known in the art (see, for example, patent application WO2013096148A).

[0062] Table 2

[0063] Stickiness Rating* illustrate 1 Non-sticky 2 ≥ 1 / 4 edge cracked and ≥ ½ cracked 3 ≥ 1 / 8 and ≤ 1 / 4 edge cracks and ≤ ½ cracks 4 Adhesive (≤1 / 8 of the outer edge cracked) 5 High viscosity

[0064] *A 1 / 2 rating is used when the result falls between two ratings on the stickiness rating scale.

[0065] Examples 9-11:

[0066] The components of the adhesive compositions of Examples 9 to 11 are shown in Table 3. All values ​​listed in Table 3 are in parts by weight of the components. As shown in Table 3, Example 10 is a comparative example containing a non-disclosed release agent; Example 11 is a comparative example without a release agent.

[0067] Table 3

[0068]

[0069] program

[0070] The particleboard ingredients for the surface layer (A) and the core layer (B) were placed in separate stainless steel silos. The silos were transferred to a blender, and the components of the adhesive composition (C) of Examples 8 to 10 were added one by one using a continuous sprayer in the following ratios (by weight): A:C = 100:14 and B:C = 100:5.5. Water was added to the blended material to control the moisture content of the surface layer to 16% and the moisture content of the core layer to 5%. The mixture of the surface layer and the core layer was initially formed into a loosely formed mat, which was then pressed between two rubber belts at room temperature and a pressure of 1 to 1.5 MPa for 10 to 30 seconds to reduce the thickness of the mat (pre-compression step), and then further pressed between two steel belts at an elevated temperature of 180 to 220°C and a pressure of 2-4 MPa for 3 to 6 minutes to form the particleboard.

[0071] The particleboards are produced according to methods known in the art (see for example patent application WO9717388A).

[0072] The physical properties of the samples were evaluated according to GBT 17657-2013.

[0073] result

[0074] Viscosity performance

[0075] like Figure 1 As shown in , different types of tackifiers can provide good tack performance compared to a blank example (Example 7) that loses tack very quickly. Compositions using copolymers of vinyl acetate as tackifiers have better tack performance (Examples 1 to 4). However, when the amount of phosphate ester is too high, it affects the tack performance (Example 2). UF is an adhesive widely used in the composite wood industry and has good tack performance (Example 8). However, UF releases formaldehyde. The adhesive compositions of the present disclosure match or exceed the tack performance of UF.

[0076] demoulding performance

[0077] like Figure 2A As shown in , the particleboard mats using the composition of the present disclosure in the pre-compression step have good demoulding properties (Example 9); Figure 2B As shown in , the particleboard mat using a release agent not disclosed herein in the pre-compression step adhered to the rubber belt (Example 10); Figure 2C As shown in , the particleboard mat without release agent in the pre-compression step adheres to the rubber belt and the surface of the mat is destroyed (Example 11).

[0078] Physical properties

[0079] Table 4

[0080]

[0081] Table 4 shows that particleboards using the compositions of the present disclosure have good physical properties (Example 9); however, particleboards using different release agents or no release agent may form poor particleboards (Example 10) or fail to form particleboards (Example 11).

Claims

1. An adhesive composition comprising: (a) a polyfunctional isocyanate or an isocyanate prepolymer, wherein the isocyanate prepolymer is obtained by reacting a polyfunctional isocyanate with a polyfunctional polyol; (b) a tackifier; and (c) phosphate esters, The tackifier is a homopolymer of vinyl acetate or a copolymer of vinyl acetate or a mixture thereof.

2. The adhesive composition according to claim 1, wherein the polyfunctional isocyanate is polymeric MDI or an MDI isomer mixture or a mixture thereof. 3 . The adhesive composition according to claim 1 , wherein the molecular weight of the tackifier is in the range of 10,000 to 2,000,000. 4 . The adhesive composition according to claim 1 , wherein the molecular weight of the tackifier is in the range of 100,000 to 1,000,000. 5 . The adhesive composition according to claim 1 , wherein the phosphate ester is an alkyl ether phosphate ester or a mixture of an alkyl phosphate ester and an alkyl ether phosphate ester. 6 . The adhesive composition according to claim 1 , wherein the molecular weight of the phosphate ester is in the range of 200 to 2000. 7 . The adhesive composition according to claim 1 , wherein the molecular weight of the phosphate ester is in the range of 300 to 1000. 8 . The adhesive composition according to claim 1 , wherein a weight ratio of the tackifier to the phosphate ester is in a range of 30:1 to 20,000:

1. 9 . The adhesive composition according to claim 1 , wherein a weight ratio of the tackifier to the phosphate ester is in a range of 500:1 to 2000:

1. 10 . The adhesive composition according to claim 1 , wherein the adhesive composition further comprises a wax.

11. A method for preparing the adhesive composition according to any one of claims 1 to 10, comprising mixing the tackifier and the phosphate ester in a first step and then adding the polyfunctional isocyanate or the isocyanate prepolymer in a second step.

12. Use of the adhesive composition according to any one of claims 1 to 10 in the preparation of composite wood.

13. The use according to claim 12, wherein the composite wood material is particle board or plywood.

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