DK200600159U3 - Adhesive System - Google Patents

Description

DK 2006 00159 U3

Title: Adhesive Voting

The present invention relates to an adhesive system comprising etherified amino resin, a polymer made of one or more ethylenically unsaturated monomers, a curing agent and a polyvinyl alcohol.

Adhesive systems suitable for use in wood-based structures for outdoor use are generally based on formaldehyde resins such as phenol-resorcinol-formaldehyde (PRF), phenol-formaldehyde (PF) and melamine-urea-formaldehyde (MUF). The main drawbacks of these adhesive systems are their long cure time at room temperature (-20 ° C) and poor bonding performance at temperatures below 20 ° C. Typical press times for these systems are in the range of 5 to 24 hours at 20 ° C. In addition, a post-curing time, especially for melamine-based resins, is required several days before the beams can be shipped to customers. These factors severely hamper natural productivity in, for example. laminated beam industries.

Furthermore, it is also known that amino resins such as urea-formaldehyde (UF) resin can be combined with dispersions of vinyl, acrylic or butadiene-styrene-type polymers to achieve improved bonding performance. Adhesives based solely on dispersions of polymers such as polyvinyl acetate are not at all suitable for use in load-bearing structures. They do not meet the standards for, for example, laminated beams. This is mainly due to their thermoplastic properties, which give creep in construction and poor durability.

EP 0 501 174 B1 discloses a cure composition for urea-formaldehyde glue containing an aqueous emulsion of a polyvinyl acetate comprising post-crosslinking groups, an ammonium salt and urea. However, this curing composition is not suitable for adhesive systems which must be cured at room temperature or at lower temperatures.

2 DK 2006 00159 U3

Thus, technical solutions are still being sought for the need to find adhesive systems that are quick-curing even at room or lower temperatures and provide designs with strong adhesive joints that meet the required standards for end-use products.

Thus, the present invention provides an adhesive system and a curing composition suitable for use in amino resin-based adhesive systems by which the above problems can be overcome.

The adhesive system of the invention is defined in the appended claims. It comprises (a) a lined amino resin, (b) a polymer made of one or more ethylenically unsaturated monomers, (c) a curing agent and (d) a polyvinyl alcohol.

The preferred amino resin used as the resin component of the adhesive system according to the invention can be any preferred amino resin, such as preferred urea-formaldehyde resin, melamine-urea-formaldehyde resin, melamine-formaldehyde resin, or preferred melamine resin. urea-phenol-formaldehyde resin. Preferred preferred amino resins are preferred melamine-urea-formaldehyde and preferred melamine-formaldehyde, and most preferably are preferred melamine-formaldehyde.

The term "preferred amino resin" as used herein refers to an amino resin which has been modified by reaction with an alcohol such as methanol, ethanol or butanol. The degree of etherification can be defined by 13 C NMR according to e.g. the following formula:

Degree of preference -

RNHCH2Q-CH3 RNHCH20 - CH3 + CH2OH

xl00%

Conveniently, the etherified amino resin has a degree of etherification of 4-95%, preferably 10-75% and most preferably 30-60%.

3 DK 2006 00159 U3

The resin component of the adhesive system may be comprised of a mixture of a lined and non-lined amino resin. Suitable non-etherified amino resins include urea-formaldehyde, melamine-urea-formaldehyde, melamine-formaldehyde and melamine-urea-phenol-formaldehyde.

The amount of lined amino resin in the resin component is suitably> 4 wt%, preferably> 50.0 wt% and most preferably £ 90.0 wt% based on the solids content of the resin component.

The total amount of the resin component of the adhesive system is suitably 10-90% by weight, preferably 40-85% by weight, and most preferably 50-80% by weight, based on the solids content of the adhesive system.

The polymer of the invention is suitably a homopolymer or copolymer made of one or more ethylenically unsaturated monomers. Examples of suitable ethylenically unsaturated monomers are vinyl monomers such as vinyl esters e.g. vinyl acetate, vinyl propionate, vinyl butyrate and comonomers thereof with e.g. ethylene; alkyl esters of acrylic and methacrylic acid such as methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, etc .; butadiene styrene and derivatives thereof, such as carboxylated butadiene styrene; substituted or unsubstituted mono and dialkyl esters of alpha, beta-unsaturated dicarboxylic acids such as substituted and unsubstituted mono and dibutyl, mono and diethyl maleate esters as well as the corresponding fumarates, itaconates and citronates; alpha-beta-unsaturated carboxylic acids such as crotonic acid, acrylic acid and methacrylic acid and mixtures thereof. Polymers based on vinyl acetate are preferred. Preferably, the polymer is prepared from at least 50% by weight of vinyl acetate based on the total weight of the monomers.

According to a preferred embodiment of the invention, the polymer comprises cross-linking groups. The post-crosslinking groups can be incorporated into the polymer by copolymerizing one or more ethylenically unsaturated monomers with at least one monomer comprising at least one post-crosslinking group.

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Suitable crosslinking groups include the groups N-alkylol, N-alkoxymethyl, carboxylate and glycidyl,

By post-crosslinking monomer is meant herein a monomer having a first reactive functional group which renders the monomer copolymerizable with one or more ethylenically unsaturated comonomers and a second functional group which does not form part of the copolymerization reaction during the polymer formation but provides a reactive site on the copolymer. which can subsequently be traded under e.g. acidic conditions with another responsive site on the copolymer and / or amino resin to cross-link the copolymer and / or amino resin.

Suitable post-crosslinking monomers include N-alkylolacrylamides, e.g. N-methylolacrylamide, N-ethanolacrylamide, N-propanol acrylamide, N-methylol methacrylamide, N-ethanol methacrylamide, N-propanol methacrylamide, N-methylol maleamide, N-methylol maleamic acid, N-methylol maleamic acid esters; N-alkylolamides of vinyl aromatic acids such as N-methylol-p-vinylbenzamide and the like; also N- (alkoxymethyl) acrylates and methacrylates wherein the alkyl group has from 1-8 carbon atoms such as N- (methoxymethyl) acrylamide, N- (butoxymethyl) acrylamide, N- (methoxymethyl) methacrylamide, N- (butoxymethyl) allyl carbamate and N- (methoxymethyl) allyl carbamate and mixtures of these monomers with allyl carbamate, acrylamide or methacrylamide; and further, triallyl cyanurate. Preferably, N-methylolacrylamide or N- (butoxymethyl) acrylamide is used.

The polymer is conveniently prepared from 0.1-10% by weight and preferably 0.2-6% by weight post-crosslinking monomer based on the total weight of monomers.

In a preferred embodiment, the copolymer is based on vinyl acetate and N-methylolacrylamide.

The amount of the polymer in the adhesive system is suitably 5-60% by weight, preferably 10-50% by weight and most preferably 15-30% by weight, based on the solids content of the adhesive system.

Mixtures of polymers containing post-crosslinking groups and polymers without post-crosslinking groups can also be used according to the invention. Eg. For example, the polymer may include both polyvinyl acetate without post-crosslinking groups and vinyl acetate-based polymer containing post-crosslinking groups.

Preferably, the polymer of the invention is used in the form of an aqueous dispersion.

Suitable curing agents include organic acids which have a fast cure rate even at room temperature (~ 20 ° C) and below. Preferred organic acids include carboxylic acids such as formic acid and maleic acid and most preferably formic acid. The curing agent may be present in the adhesive system in an amount of suitably 2-40 wt%, preferably 5-20 wt% and most preferably 7-15 wt% based on the solids content of the adhesive system.

Although polyvinyl alcohol is initially present in polyvinyl acetate (PVAc) dispersions in an amount of 4-6% by weight, it has been found in the present invention that an additional addition of PVA to the adhesive system is present in addition to what is initially present. in the PVAc dispersion, further improves the water resistance and adhesive bonding strength of the finished products. Conveniently, the polyvinyl alcohol used has a degree of hydrolysis> 75% and may be present in the adhesive system in an amount of 0.1-20% by weight, preferably 1-10% by weight, and most preferably 3-7% by weight, based on the solids content of the adhesive system. Thus, the total amount of PVA in the adhesive system including PVA initially present in the PVAc dispersion could be as high as 7-14% by weight based on the adhesive system solids.

In a preferred embodiment of the invention, components b) -d) are blended into a component e) which thus constitutes a curing composition.

The adhesive system may also include fillers or additives such as glycol suitable for the desired final use of the adhesive system.

The solids content of the adhesive system may conveniently be 20-80% by weight, preferably 30-70% by weight and most preferably 45-65% by weight. The remaining part up to 100% by weight consists of water.

The term "adhesive system" as used herein means a curing formulation of a resin and a curing component and other suitable additives.

The claimed invention provides adhesive systems which have improved pressing and post-curing times, water resistance and adhesive joint strength even when cured at room temperature or below. These adhesive systems are suitable for bonding wood-based products and preferably wood-based products for outdoor use, e.g. laminated beams, finger joints and l-beams.

The curing composition of the invention is defined in the appended claims. It comprises (b) a polymer made from one or more ethylenically unsaturated monomers, which monomer contains crosslinking groups, (e) a carboxylic acid and (d) a polyvinyl alcohol.

The polymer is a copolymer of one or more ethylenically unsaturated monomers and at least one monomer containing at least one crosslinking group.

Suitable ethylenically unsaturated monomers and monomers comprising cross-linking groups for use in preparing the polymer of the invention are described above.

The amount of the polymer in the curing composition is suitably 3-85 wt%, preferably 25-70 wt% and most preferably 45-65 wt% based on the solids composition of the curing composition. Preferably, the polymer is used in the form of an aqueous dispersion.

The use of a carboxylic acid, which is preferably maleic or formic acid, provides a fast-curing curing composition even at room temperature or below.

Suitable amounts of acid in the curing composition are 2-50 wt%, preferably 10-50 wt% and most preferably 20-35 wt% based on the solids composition of the curing composition.

Preferably, a polyvinyl alcohol having a degree of hydrolysis> 75% is used. It is present in an amount of 0.1-40% by weight, preferably 4-30% by weight and most preferably 8-15% by weight, based on the hardener composition solids. Addition of additional polyvinyl alcohol in addition to that which may be present in e.g. a PVAc-based aqueous polymer dispersion, provides a further improved water resistance and adhesive properties to the adhesive system using the claimed curing composition.

If desired, the curing composition may also comprise fillers or other additives such as glycol suitable for the desired final use of the curing composition.

The solids content of the curing composition may conveniently be 5-80% by weight, preferably 10-60% by weight and most preferably 30-50% by weight. The remaining part up to 100% by weight consists of water.

The term "solids" (of the adhesive system and the curing composition) as used herein also includes the weight of the pure acid used as a curing agent, even in the case where the curing agent is a volatile acid such as formic acid.

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The claimed curing composition is suitable for use in formulating adhesive compositions based on amino resins, resulting in water-resistant and creep-resistant adhesive systems which ensure structures with strong adhesive joints.

Although liquid adhesive systems, ie. where the resin component and the curing component are in liquid form preferred by the invention, powdery adhesive systems, i.e. wherein the resin component and / or curing component is in powder form.

The invention is further illustrated by the following non-limiting examples. Parts and percentages relate to parts by weight and percentages, respectively, unless otherwise stated.

Examples In the examples of the invention, as the component a), a lined melamine-formaldehyde (EMF) resin having a degree of etherification of 46% and having a solids content of 68-72% is used. In the Comparative Examples, as a component a) a non-lined melamine-formaldehyde (MF) resin having a solids content of 63-68% was used. Two different aqueous dispersions were used, one based on a polyvinyl acetate polymer containing cross-linking groups (PVAc-X) and the other based on a conventional polyvinyl acetate polymer without cross-linking groups (PVAc).

Example 1: The composition of the hardener used is shown below in Table 1. The resin component used was MF lined.

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Table 1

Component Weight% based on the total weight of the curing composition PVAc-X dispersion 22% Formic acid 11% Polyvinyl alcohol 5% Water 62% 5 Example 2 (Comparison): The same curing composition was used as in Example 1 and the resin component used was non-enriched MF .

Example 3: The composition of the hardener used is shown below in Table 2.

Component Weight% based on the total weight of the curing composition PVAc-X dispersion 27% Formic acid 11% Polyvinyl alcohol 0% Water 62%

Example 4 (Comparison): The same hardener composition 15 was used as in Example 3 and the resin component used was non-preferred MF.

Example 5: The composition of the hardener used is shown below in Table 3. The resin component used was lined MF.

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Table 3

Component Weight% based on the total weight of the curing composition PVAc 27% Formic acid 11% Polyvinyl alcohol 0% Water 62%

Example 6 (Comparison): The same hardener composition 5 as in Example 5 was used and the resin component used was non-lined MF.

Example 7: The composition of the hardener used is given below in Table 4. The resin component used was MF lined.

Table 4

Component Weight% based on the total weight of the curing composition PVAc dispersion 22% Formic acid 11% Polyvinyl alcohol 5% Water 62%

Example 8 (Comparison): The same curing composition as in Example 7 was used and the resin component used was non-lined MF.

15

The resin component and the curing component of the above-described examples of adhesive systems were applied separately in a 1: 1 mixing ratio of 90 cm x 15.5 cm pieces of spruce wood and in an amount of 350 g / m2. Then, laminates were formed from the pieces which were pressed at a temperature of 20 ° C, a pressure of 8 bar and a relative humidity of 60% for 2 hours. After 36 hours 11 DK 2006 00159 U3 post-cure time, the laminates for delamination were tested according to standard EN 391 B. The results are shown in Table 5 below.

Table 5

Adhesive System of Delamination Example 1 0.3% Example 2 0.61% Example 3 9.7% Example 4 14.1% Example 5 30.5% Example 6 82.1% Example 7 10.0% Example 8 28.2 %

It is evident that the claimed adhesive systems provide improved adhesive joints over prior art adhesive systems.

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Bruas Model Claims 1. An adhesive system new in that it comprises (a) a resin component comprising a lined amino resin, (b) a polymer made of one or more ethylenically unsaturated monomers, (c) a curing agent, and 8d) a polyvinyl alcohol.

A hardener composition for amino resin type bonding systems new in that it comprises (b) a polymer made of one or more ethylenically unsaturated monomers, each polymer containing post-crosslinking groups, (c) a carboxylic acid and (d) a polyvinyl alcohol .

The adhesive system of claim 1, which is new in that the amount of the resin component of the adhesive system is 10-90% by weight based on the solids of the adhesive system.

The adhesive system according to any one of claims 1 or 3, which is new in that the amount of the resin component of the adhesive system is 40-85% by weight based on the solids of the adhesive system.

The adhesive system according to any one of claims 1 or 3-4, which is new in that the amount of the resin component of the adhesive system is 50-80% by weight based on the solids of the adhesive system.

The adhesive system according to any one of claims 1 or 3-5, which is new in that the amount of the polymer in the adhesive system is 5-60% by weight based on the solids of the adhesive system.

The adhesive system according to any one of claims 1 or 3-6, which is new in that the amount of the polymer in the adhesive system is 10-50% by weight based on the solids of the adhesive system.

Adhesive system according to any one of claims 1 or 3-7, which is new in that the amount of polymer in the adhesive system is 15-30% by weight based on the solids of the adhesive system.

Adhesive system according to any one of claims 1 or 3-8, which is new in that the curing agent is present in the adhesive system in an amount of 2-40% by weight based on the solids of the adhesive system.

The adhesive system according to any one of claims 1 or 3-9, which is new in that the curing agent is present in the adhesive system in an amount of 5-20% by weight based on the solids of the adhesive system.

Adhesive system according to any one of claims 1 or 3-10, which is new in that the curing agent is present in the adhesive system in an amount of 7-15% by weight based on the solids of the adhesive system.

Adhesive system according to any one of claims 1 or 3-11, which is new in that the polyvinyl alcohol is present in the adhesive system in an amount of 0.1-20% by weight based on the solids of the adhesive system.

Adhesive system according to any one of claims 1 or 3-12, which is new in that the polyvinyl alcohol is present in the adhesive system in an amount of 1-10 wt% based on the solids of the adhesive system.

Adhesive system according to any one of claims 1 or 3-12, which is new in that the polyvinyl alcohol is present in the adhesive system in an amount of 3-20% by weight based on the solids of the adhesive system.

An adhesive system according to any one of claims 1 or 3-14, which is new in that the polyvinyl alcohol is present in the adhesive system in an amount of 3-10% by weight based on the solids of the adhesive system.

An adhesive system according to any one of claims 1 or 3-15, which is new in that the polyvinyl alcohol is present in the adhesive system in an amount of 3-7% by weight based on the solids of the adhesive system.

The adhesive system according to any one of claims 1 or 3-16, which is new in that the amount of lined amino resin in the resin component is> 4% by weight.

An adhesive system according to any one of claims 1 or 3 to 17, which is new in that the amount of lined amino resin in the resin component is> 50% by weight.

An adhesive system according to any one of claims 1 or 3-18, which is new in that the amount of lined amino resin in the resin component is> 90% by weight.

Adhesive system according to any one of claims 1 or 3-19, which is new in that the polymer is prepared from 0.1 to 10% by weight of post-crosslinking monomer, based on the total weight of monomers.

An adhesive system according to any one of claims 1 or 3 to 20, which is new in that the polymer is prepared from 0.2 to 6% by weight of post-crosslinking monomer, based on the total weight of monomers.

An adhesive system according to any one of claims 1 or 3-21, which is new in that the etherified amino resin has a degree of etherification of 4 to 95%.

The adhesive subsystem of any one of claims 1 or 3 to 22, which is new in that the etherified amino resin has a degree of etherification of 10 to 75%.

The adhesive system of any one of claims 1 or 3 to 23, which is new in that the etherified amino resin has a degree of ethericity of 30 to 60%, an adhesive system according to any one of claims 1 or 3-24, which is new in that the preferred amino resin is a laminated melamine-formaldehyde resin or a laminated uramine-formaldehyde resin.

An adhesive system according to any one of claims 1 or 3-25 or a curing composition according to claim 2, which is new in that the polymer is a homopolymer or copolymer made from one or more monomers selected from the group consisting of vinyl esters, alkyl esters of acrylic acid and methacrylic acid, mono- and dialkyl esters of alpha-beta-unsaturated dicarboxylic acids, alpha-beta-unsaturated carboxylic acids, styrene-butadiene and derivatives thereof and mixtures thereof.

An adhesive system according to any one of claims 1 or 3-26 or a curing composition according to claim 2 or 26, which is new in that the polymer is a homopolymer or copolymer based on vinyl esters.

An adhesive system according to any one of claims 1 or 3-27 or a curing composition according to claim 2 or 27, which is new in that the polymer is a homopolymer or copolymer based on vinyl acetate.

Adhesive system according to any one of claims 1 or 3-28, which is new in that the polymer comprises post-crosslinking groups.

An adhesive system according to claim 29 or a curing composition according to any one of claims 2 or 26-28, which is new in that the post-crosslinking groups are incorporated into the polymer by copolymerizing one or more ethylenically unsaturated monomers with at least one monomer. comprising at least one post-crosslinking group.

An adhesive system according to any one of claims 1 or 3-30 or a curing composition according to any of claims 2, 26-28 or 30, which is new in that the polymer is a copolymer of vinyl acetate. and N-methylol acrylamide.

An adhesive system according to any one of claims 1 or 3-31, which is new in that the curing agent is a carboxylic acid.

An adhesive system according to claim 32 or a curing composition according to any one of claims 2, 26-28 or 30-31, which is new in that the carboxylic acid is formic or maleic acid.

Adhesive system according to any one of claims 1 or 3-33 or curing composition according to any of claims 2, 26-28, 30-31 or 33, which is new in that the polyvinyl alcohol has a degree of hydrolysis of> 75% .

A curing composition according to any one of claims 2, 26-28, 30-31 or 33-34, which is new in that the amount of the polymer in the curing composition is 25-70% by weight based on the curing composition solids.

A curing composition according to any one of claims 2, 26-28, 30-31 or 33-35, which is new in that the amount of the polymer in the curing composition is 45-65% by weight based on the curing composition solids.

The curing composition of any of claims 2, 26-28, 30-31 or 33-36, which is new in that the amount of acid in the curing composition is 2-50% by weight based on the curing composition solids.

The curing composition of any of claims 2, 26-28, 30-31 or 33-37, which is new in that the amount of acid in the curing composition is 10-50% by weight based on the curing composition solids.

Curing composition according to any one of claims 2, 26-28, 30-31 or 33-38, which is new in that the amount of acid in the curing composition is 20-35% by weight based on the curing composition solids.

A curing composition according to any one of claims 2, 26-28, 30-31 or 33-39, which is new in that the amount of polyvinyl alcohol in the curing composition is 0.1-40% by weight based on the curing composition solids.

The curing composition according to any one of claims 2, 26-28, 30-31 or 33-40, which is new in that the amount of polyvinyl alcohol in the curing composition is 4-40% by weight based on the curing composition solids.

The curing composition of any one of claims 2, 26-28, 30-31 or 33-40, which is new in that the amount of polyvinyl alcohol in the curing composition is 4-30% by weight based on the curing composition solids.

The hardener composition according to any of claims 2, 26-28, 30-31 or 33-42, which is new in that the amount of polyvinyl alcohol in the hardener composition is 4-15% by weight based on the hardener composition solids.

44. Curing composition according to any one of claims 2, 26-28, SO-SI or 33-41, which is new in that the amount of polyvinyl alcohol in the curing composition is 8-40% by weight based on the curing composition solids.

The hardener composition according to any one of claims 2, 26-28, 30-31 or 33-42 or 44, which is new in that the amount of polyvinyl alcohol in the hardener composition is 8-30% by weight based on the hardener composition solids.

46. Curing composition according to any one of claims 2, 26-28, 30-31 or 33-45, which is new in that the amount of polyvinyl alcohol in the curing composition is 8-15% by weight based on the hardener composition of the curing composition.

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