JPH0355514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive composition having water resistance and excellent stability, and is particularly useful as a wood adhesive.

Currently, water-soluble formalin-based condensation resins such as urea resin, melamine resin, phenolic resin, etc. are used as adhesives for plywood or secondary processing of plywood, chipboard, laminated wood, etc. Formaldehyde, which is generated during the application process of adhesives or remains in products using these adhesives, may be undesirable from an environmental health perspective.

Conventionally, there has been a technology in which organic polyisocyanate is used in combination with other organic hydrophilic solvents or surfactants for the purpose of suppressing formalin release from formalin-based adhesives and enhancing water resistance, as disclosed in JP-A-49-
As described in No. 22438 and JP-A No. 50-69134, when using these in an aqueous solvent, it is extremely difficult to disperse polyisocyanate alone, and even by forced stirring, it is difficult to disperse the polyisocyanate uniformly in large processed products. It was difficult to obtain sex.

The inventors of the present invention conducted extensive research with the greatest goal of improving these drawbacks, and as a result, they discovered that the above drawbacks could be improved by using a self-emulsifying polyisocyanate in combination with a formalin-based condensation resin.

That is, the present invention provides an adhesive composition comprising a self-emulsifying polyisocyanate and a formalin-based condensation resin, in which the self-emulsifying polyisocyanate has the general formula RO(CH ₂ CH ₂ O)n CONHX (wherein R is carbon An alkyl group having 1 to 4 atoms,
n is an integer such that the compound contains on average at least 5 oxyethylene groups, and
is the residue of a di- or polyisocyanate and contains at least one free isocyanate)
This is a wood adhesive composition characterized by using a mixture of a nonionic surfactant and an organic polyisocyanate shown in the following.

The greatest feature of the present invention is that by using self-emulsifying polyisocyanate and dispersing and emulsifying a polyisocyanate component that is highly reactive with active hydrogen atoms in water, fine particles whose active isocyanate surface is coated with a polyurea compound are produced. , and temporarily suppress its reaction activity, making it easier to use it in combination with formalin-based condensation resins.

Furthermore, the use of self-emulsifying polyisocyanates reduces the absolute amount of formalin released during wood processing or from products using these adhesives, thereby reducing environmental pollution problems.

Further, by using a formalin-based condensation resin and a self-emulsifying polyisocyanate in combination, it is possible to significantly improve the deterioration of various wood products over time, such as water resistance.

The self-emulsifying polyisocyanate used in the present invention has a high effective NCO content, low viscosity, and good water dispersibility.
RO(CH ₂ CH ₂ O)n CONHX (wherein R is an alkyl group having 1 to 4 carbon atoms, and n is an integer such that the compound contains on average at least 5 oxyethylene groups) , and X is a residue of di- or polyisocyanate, and at least one
A mixture of a nonionic surfactant (containing 10 free isocyanates) and an organic polyisocyanate with a molecular weight of 500 to 1500.
A mixture of a nonionic surfactant whose terminal group is an isocyanate group and the above polyphenylmethane polyisocyanate obtained by reacting methoxypolyethylene glycol with polyphenylmethane polyisocyanate containing 20% by weight or more of diisocyanate, and NCO The content is within the range of 28-30 weight percent.

Further, in the present invention, one type or a mixture of two or more types of self-emulsifying polyisocyanates can be used.

The formalin-based condensation resin used in the present invention includes urea-formalin-based resin, melamine-formalin-based resin, phenol-formalin-based resin, etc., and these may be one type, a combination of two or more types, or a co-condensate thereof. .

Conventionally, these formalin-based condensation resins are generally commercially available in powder or liquid form, and when used, they are diluted with water or other solvents or used in liquid form, but in this case, the solid content is generally 10 parts by weight. %
It is often used in a range of 70 parts by weight.

When using these resins alone for bonding, add a curing agent, additive, or thickener suitable for each resin, apply it to the object to be bonded, press it at room temperature or at a heated temperature, etc. It was finally cured to obtain adhesive strength.

Normally, formalin adhesives are used at a solid content of about 50% and often contain about 50% water, so it is necessary to dry the adherend in order to shorten the heat pressing time. be.

However, since self-emulsifying polyisocyanates can be emulsified with water at any ratio, the ratio of water included when applying the glue can be easily adjusted, which can shorten the drying process of the adherend and allow for acceptable moisture content. It has the advantage of having a wide range.

The resin concentration of the adhesive according to the invention is 10 parts by weight
It can be used in a range of 70 parts by weight.

The self-emulsifying polyisocyanate/formalin condensation resin can be mixed in almost any ratio, but in the present invention, a weight ratio of 1/10 to 10/10 is preferred.

When using this adhesive composition, the self-emulsifying polyisocyanate and formalin-based condensation resin may be mixed in advance and applied to the adherend, or the mixture ratio may be adjusted using a two-component simultaneous injection device. A product can be easily obtained by applying the adhesive to an object to be adhered and then compressing it using a press or the like at room temperature or under heating. In addition, when using the present adhesive composition, known fillers such as gypsum, clay, talc, blood powder, soybean powder, wheat flour, and aluminum hydroxide can also be used.

These additives that help control curing are the constituent resin components.
It can be used in a range of 1 to 30 parts by weight per 100 parts by weight, but it is preferably 1 to 20 parts by weight.

Also, various conditions for curing, such as temperature, time,
To adjust the pressure, etc., acids, salts, bases, etc. can be added to the components.

Next, the present invention will be further explained in detail with reference to Examples, but the present invention is not limited to these Examples.

Note that parts and % in Examples and Comparative Examples indicate parts by weight and % by weight, respectively.

Example 1 Coronate 3053 (trade name, manufactured by Nippon Polyurethane Industries, Ltd., a self-emulsifying polyisocyanate) was added to 50 parts of water.
75 parts (NCO content: 29.4% or less) were added and mixed by stirring at 1000 rpm using a stirrer to obtain polyisocyanate emulsion A solution.

Next, urea resin (Oshika Shinko Co., Ltd. No. 170B, solid content 66
(same below) 300 parts of 20% ammonium chloride aqueous solution 24
and mixed at 1000 rpm using a stirrer to obtain urea resin solution B.

120 parts of polyisocyanate emulsion solution A were added to 262 parts of urea resin solution B and mixed well at 1000 rpm using a stirrer to obtain a blended paste solution (1).

This was used as an adhesive, and while being mixed using a blender, it was sprayed onto wood chips (lauan) under the following conditions to prepare particle board.

Spray removal conditions Isocyanate content 3.5% Urea resin content 7.8% Hot press conditions Pressure 40Kg/cm ² , Temperature 120℃, Time 15 seconds/mm (pressure time per 1mm of board) Physical properties Normal bending strength ¹⁾ 215Kg/ ^cm 2Bending strength after boiling1 ⁾
82Kg/cm ² (Strength retention rate 40%) Comparative example 1 Using the same method as Example 1, the oil content was determined using only urea resin.
The physical properties of the board obtained by treatment with 11.25% were as follows.

Normal bending strength ¹⁾ 205Kg/cm ^2Bending strength after boiling ¹⁾ 0Kg/cm ^2Example 2 Gradually add 30 parts of water to 20 parts of wheat flour and mix well.
This was prepared by adding 100 parts of the mixed size solution (1) obtained in Example 1 and stirring and mixing at 1000 rpm using a stirrer.
I got (2). Using this as an adhesive, plywood was prepared under the following conditions.

Red lauan veneer composition 1.0+1.5+1.0mm Coating amount 36g/30×30cm Cold press Pressure 10Kg/cm ² , Time 100 seconds Hot press Pressure 10Kg/cm ² , Temperature 105℃, Time 240 seconds Adhesive strength Normal adhesive strength ²⁾ 18.4Kg/cm ² Wood breakage rate 100% Repeated boiling adhesive strength ²⁾
11.0Kg/cm ² Wood breakage rate 61% Comparative example 2 Gradually add 40 parts of wheat flour and mix well. Add 100 parts of urea resin and 0.3 parts of ammonium chloride to this, stir and mix at 1000 rpm with a stirrer to make a blended paste liquid. A plywood was prepared in the same manner as in Example 2.

Adhesive strength Normal adhesive strength ²⁾ 15.5Kg/cm ² Wood breakage rate 50% Boiled repeated adhesive strength ²⁾ 0Kg/cm ² Wood breakage rate 0% Example 3 Add 50 parts of Coronate 3053 to 50 parts of water and use a stirrer. The mixture was stirred and mixed at 1000 rpm to obtain a polyisocyanate emulsion C solution.

Separately, melamine urea cocondensation resin (Aikayuri UM-82 manufactured by Aika Kogyo, solid content 51% or less) 100
10 parts of a 20% ammonium chloride aqueous solution was added to the mixture and mixed by stirring at 1000 rpm using a stirrer to obtain a melamine urea cocondensation resin solution D.

100 parts of polyisocyanate emulsion solution C was added to 110 parts of solution D, and the mixture was thoroughly mixed with a stirrer at 1000 rpm to obtain a blended paste solution.

Using this as an adhesive, plywood was prepared under the following conditions.

Veneer veneer 2.0mm 3 ply Application amount 40g/30×30cm Cold press Pressure 10Kg/cm ² , Time 100 seconds Hot press Pressure 10Kg/cm ² , Temperature 110℃, Time 10 minutes Adhesive strength Normal adhesive strength ²⁾ 18.5Kg/cm ² Wood breakage rate: 100% Continuous boiling adhesive strength2 ⁾ 10.5Kg/cm ^2Wood breakage rate: 70% Comparative example 3 Add 10 parts of a 20% ammonium chloride aqueous solution to 100 parts of melamine urea co-condensed resin and mix well to obtain a blended glue solution. Ta.

This mixed size solution was treated in the same manner as in Example 3 to prepare plywood.

Adhesive strength Normal adhesive strength ²⁾ 16.3Kg/cm ² Wood breakage rate 90% Continuous boiling adhesive strength ²⁾ 6.5Kg/cm ² Wood breakage rate 20% Example 4 Add 75 parts of Coronate 3053 to 100 parts of water and mix in a stirrer. The mixture was stirred and mixed at 1000 rpm to obtain polyisocyanate emulsion E solution.

Separately, 30 parts of water was gradually added to 10 parts of soybean flour and mixed well, and to this was added 100 parts of water-soluble phenol resin (Aika Neoresin P-73, manufactured by Aika Kogyo, solid content 53%),
0.1 part of caustic soda was added and mixed well with a stirrer at 1000 rpm to obtain a water-soluble phenol F solution.

Add 90 parts of water-soluble phenol F solution to 35 parts of polyisocyanate emulsion E solution, and mix with a stirrer.
The mixture was thoroughly mixed at 1000 rpm to obtain a blended paste solution. Using this as an adhesive, plywood was prepared under the following conditions.

Veneer veneer 1.0mm 3-ply application amount 30g/30×30cm Cold press Pressure 10Kg/cm ² , Time 100 seconds Hot press Pressure 10Kg/cm ² , Temperature 135℃, Time 180 seconds Adhesive strength Normal adhesive strength ²⁾ 18.8Kg/cm ² Wood breakage rate: 100% Hot and cold water adhesive strength ²⁾ 16.0 Kg/cm ² Wood breakage rate: 55% Comparative Example 4 Plywood was prepared in the same manner as in Example 4 using water-soluble phenol F solution.

Adhesive strength Normal adhesive strength ²⁾ 16.5 Kg/cm ² Wood break rate 15% Hot and cold water adhesive strength ²⁾ 12.3 Kg/cm ² Wood break rate 0% 1) JISA5908 2) JIS ordinary plywood method comparison example 5 Water-soluble phenol F liquid To 90 parts, add 26.3 parts of a solution consisting of 10 parts of an adduct of 1 mole of trimethylolpropane and 3 moles of 2,4-tolylene diisocyanate and 7.5 parts of ethyl acetate, and mix well with a stirrer at 1000 rpm to obtain a blended paste solution. Obtained. Plywood was prepared in the same manner as in Example 4 using this as an adhesive.

Adhesive strengthNormal adhesive strength2 ⁾ 15.0Kg/ ^cm2Wood damage rate 55%Hot and cold water adhesive ^strength2) 12.6Kg/ ^cm2Wood damage rate 10%

Claims (1)

[Claims] 1. In an adhesive composition comprising a self-emulsifying polyisocyanate and a formalin-based condensation resin, the self-emulsifying polyisocyanate has the general formula
RO(CH ₂ CH ₂ O)n CONHX (wherein R is an alkyl group having 1 to 4 carbon atoms, and n is an integer such that the compound contains on average at least 5 oxyethylene groups) , and X is a residue of di- or polyisocyanate, and at least one
A wood adhesive composition characterized in that it uses a mixture of a nonionic surfactant (containing 2 free isocyanates) and an organic polyisocyanate.