JPH0571045B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an aqueous dispersion of an organic polyisocyanate compound that has a stable dispersion state and is unlikely to excessively penetrate into a porous substrate, and its uses. These are binder compositions for wood chips, wood fibers, scrap urethane foam, etc., and adhesives for wood, paper, cloth, etc. [Prior art] Organic polyisocyanate compounds form strong bonds with active hydrogen groups, so they are suitable for bonding and adhering base materials with active hydrogen groups such as wood chips, wood fibers, scrap urethane foam, wood, paper, and cloth. Attempts are being made to utilize it. The organic polyisocyanate compound is usually applied to the substrate by spraying, or if the substrate is flaky or fibrous, it is applied onto a moving substrate and the organic polyisocyanate compound is applied by collision with the substrate during movement. Generally, a method of dispersion coating is used. However, organic polyisocyanate compounds have a relatively high viscosity, and the viscosity changes depending on the liquid temperature, and the lower the temperature, the higher the viscosity. Therefore, with this coating method, it is difficult to uniformly coat the substrate under varying conditions during the coating process. It is difficult to do this, and the method is to dilute it with a solvent that does not have or has weak reactivity with isocyanate groups to lower the viscosity, or to emulsify it with a surfactant and apply it as a dispersion to lower the viscosity. It is taken. When using a composition containing an organic polyisocyanate compound whose viscosity has been reduced by such a method as a binder, the solvent or dispersion medium may naturalize during the adhesion/curing process, or the organic polyisocyanate compound and the base material/solvent may Alternatively, since carbon dioxide gas is generated by reaction with a dispersion medium, it is necessary to efficiently remove the generated vapors and gases in order to develop strong adhesion and bonding. Therefore, when the organic polyisocyanate compound-containing composition is used as a binder or adhesive, the adherend substrate or the resulting adhesive product itself is usually porous. [Problems to be Solved by the Invention] However, when bonding and adhering a porous adhering material to a substrate using a composition containing a low-viscosity organic polyisocyanate compound, as described above,
This solves the problems of uneven coating and poor adhesive performance due to generated vapors and gases, but excessive penetration of the low-viscosity binder or adhesive composition into the porous adherend substrate can be solved. This results in the problem that sufficient adhesive performance may not be obtained, or that a large amount of binder or adhesive composition must be used in order to develop sufficient adhesive performance. Furthermore, if the substrate temperature or the environmental temperature during application is high, the viscosity of the binder or adhesive composition will decrease further, which will likely promote excessive penetration problems, and if the substrate has a high moisture content. A similar problem occurs when the material has a high affinity for the solvent or dispersion medium. Therefore, the conventional techniques have been insufficient from the viewpoint of easily and uniformly applying the adhesive to a porous adherend base material and obtaining sufficient adhesion and bonding. The purpose of the present invention is to provide an aqueous dispersion of an organic polyisocyanate compound that can be applied uniformly to a substrate even under varying conditions during the coating process, and that does not cause problems due to excessive penetration even when using porous adherends. It's about getting a body. [Means for Solving the Problems] In accordance with the above objective, the present inventor conducted extensive studies and arrived at the present invention. That is, it is an organic polyisocyanate compound dispersion containing xanthan gum and an isocyanate compound, characterized in that water or a mixture of a water-soluble organic solvent and water is used as a dispersion medium. The xanthan gum of the present invention is a natural gum that is sold by fermenting sugars using special microorganisms.
It is a water-soluble polymer with more than 1 million molecules, and its solution in water or a mixture of water and a water-soluble organic solvent is
Even at low concentrations, they generally exhibit high viscosity and at the same time exhibit thixotropic properties. Furthermore, it has a unique property that the viscosity of the solution is almost constant regardless of the solution temperature. Such viscosity and properties have an important meaning for the present invention. The present inventor has discovered that when an aqueous dispersion of an organic polyisocyanate compound is prepared using a xanthan gum solution having such a viscosity, the aqueous dispersion of an organic polyisocyanate compound prepared during the period from preparation to curing while having fluidity. It was found that similar viscosity was developed. When an aqueous dispersion of an organic polyisocyanate compound exhibits such thixotropic properties, under conditions where the dispersion is subjected to shear during preparation and application, the viscosity becomes low and uniform preparation and application are possible; Once it adheres to the base material, it becomes highly viscous, making it difficult to cause excessive penetration. In addition, since the viscosity of the organic polyisocyanate compound dispersion does not depend on temperature,
Even when used in a high-temperature atmosphere or on a high-temperature base material, it has the advantage of being less likely to cause excessive penetration when it adheres to the base material after application. Although thixotropic viscosity behavior can be obtained by using starch, carboxymethylcellulose, etc. instead of xanthansum, the viscosity of the organic polyisocyanate compound dispersion depends on temperature.
When applied to a high-temperature substrate, there is a problem in that it tends to over-penetrate into the substrate. Although xanthan gum is obtained by microbial fermentation, there are no particular restrictions on its purity, etc., as long as it exhibits the above-mentioned properties as an aqueous solution. There are no particular limitations on the method for preparing a solution of xanthan gum in water or a mixture of a water-compatible organic solvent and water. However, in general, when the xanthan gum referred to in the present invention is dispersed in water, it tends to produce so-called mama flour, which may impede uniform dispersion and subsequent uniform dissolution. In such a case, do not dissolve the xanthan gum, but disperse the xanthan gum in advance in an organic solvent that is compatible with water, and then add water to the dispersion, or mix and dissolve the dispersion by adding the dispersion to water. If so, problems such as those mentioned above can be avoided. As the organic solvent, methanol, ethanol, isopropanol, acetone, ethylene glycol, etc. can be used, although it varies depending on the type of water-soluble polysaccharide used. Alternatively, instead of preparing a xanthan gum solution in advance and subjecting it to the emulsification of the organic polyisocyanate compound as described above, xanthan gum, water, a surfactant, and the organic polyisocyanate compound may be simultaneously mixed and emulsified during emulsification. . The concentration of xanthan gum in a solution of xanthan gum in water or a mixture of a water-compatible organic solvent and water is preferably 0.01% by weight or more and less than 5% by weight. If the amount is less than 0.01% by weight, the effects of the present invention will not be achieved, and if it is more than 5% by weight, the organic polyisocyanate compound aqueous dispersion obtained by implementing the present invention will have too high a viscosity and will be difficult to handle. This is inappropriate. It is desirable to use the organic solvent added for the above-mentioned purpose in an amount of about 2 to 10 times the amount of the water-soluble polysaccharide. Even if it is contained, it does not pose a problem. The organic polyisocyanate compound referred to in the present invention is a compound having two or more isocyanate groups in the molecule, such as aliphatic polyisocyanate such as hexamethylene diisocyanate, m-
or p-phenylene diisocyanate, 2,
Aromatic polyisocyanates such as 4- or 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, naphthylene-1,5-diisocyanate, alicyclic polyisocyanates such as bis-(isocyanatecyclohexyl)methane, and isophorone diisocyanate. isocyanate,
Crude products of aliphatic, aromatic, and alicyclic polyisocyanates such as crude diphenylmethane diisocyanate (also referred to as polymethylene polyphenyl polyisocyanate and polymeric MDI), crude tolylene diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, and polyols. These include modified diphenylmethane diisocyanate, a modified aliphatic, aromatic, and alicyclic polyisocyanate such as a reaction product of trimethylolpropane and hexamethylene diisocyanate, and a mixture of two or more of these may be used. Among them, crude diphenylmethane diisocyanate is the most useful in terms of economy and safety in use. Examples of the nonionic surfactant in the present invention include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene acyl ester, etc. Monofunctional alkoxypolyalkylene glycols are most useful from the viewpoint of stability and stability after emulsification. The amount of nonionic surfactant added to the organic polyisocyanate compound is preferably 0.1% by weight or more and 10% by weight or less. 0.1
If it is less than 10% by weight, it is difficult to obtain a stable aqueous dispersion, and if it exceeds 10% by weight, adhesives and
When used as a binder, there is a high possibility that water resistance will be poor. The nonionic surfactant may be added during the preparation of the aqueous dispersion of the organic polyisocyanate compound, or it may be added in advance to a solution of the water-soluble polysaccharide in water or a mixture of water and an organic solvent that is compatible with water. ,
Alternatively, it may be added to the organic polyisocyanate compound. When the nonionic surfactant has reactivity with isocyanate groups, it may be reacted in advance and then made into an aqueous dispersion. There are no particular limitations on the method for preparing the organic polyisocyanate compound aqueous dispersion.
A known emulsification method may be used. In carrying out the present invention, for example, fillers, mold release agents, preservatives, fungicides, insect repellents, flame retardants,
Additives such as antioxidants and water forming agents, and modifiers such as water-soluble resins such as aqueous emulsions, latexes, and formaldehyde condensation resins may be mixed and used as necessary. [Effects of the Invention] As described above, when the aqueous dispersion of an organic polyisocyanate compound of the present invention is used, the workability during the coating process is excellent, and it is possible to avoid excessive coating on porous substrates such as wood, paper, cloth, and various foams. This has the effect of preventing the infiltration of the adhesive and, in turn, exhibiting high adhesive performance. Therefore, the organic polyisocyanate compound aqueous dispersion of the present invention can be widely used for adhesion/bonding when at least one of the materials is a porous material. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these in any way. Parts and % in the examples refer to parts by weight and % by weight, respectively, unless otherwise specified. Reference example Diethylene glycol monomethyl ether
219.0 parts and 4.45 parts of potassium hydroxide were placed in an autoclave, the temperature was raised to 90°C under nitrogen gas, and 1130 parts of ethylene oxide were reacted under pressure, followed by further reaction with 320 parts of propylene oxide, and the resulting reaction The product was neutralized with a theoretical amount of phosphoric acid and filtered to obtain a monofunctional alkoxy polyalkylene glycol. 50 parts of the obtained monofunctional alkoxy polyalkylene glycol and Mitsui Toatsu Chemical Co., Ltd.
950 parts of MDI CR-400 at 80℃ under nitrogen atmosphere
A water-dispersible MDI was obtained by a time reaction. Example: After dispersing 1 part of industrial kesanthan gum (manufactured by Dainippon Pharmaceutical Co., Ltd.) in 40 parts of methanol, water
An aqueous solution of xanthan gum was prepared by adding 460 parts of xanthan gum and stirring thoroughly to dissolve it. To the prepared solution, 330 parts of the water-dispersible MDI obtained in Reference Example was added under stirring to obtain an organic polyisocyanate aqueous dispersion. The viscosity of this organic polyisocyanate aqueous dispersion was measured using a B-type viscometer, and the results were as follows: it exhibited cyclotropic viscosity and showed a slight change in viscosity due to temperature changes. Liquid temperature Rotation speed Viscosity measurement result 25℃ 60RPM 1.3 poise 25℃ 0RPM 7.1 poise 40℃ 60RPM 1.3 poise In addition, 159g of the obtained organic polyisocyanate water dispersion was uniformly added to 950g of needle-shaped wood chips with a water content of 5.0% at room temperature. After spraying and evenly distributing it within a 30 cm square frame, the frame was removed, and the mixture was inserted between hot plates at 160°C and heated and pressed for 5 minutes to a thickness of 15 mm to obtain a park takele board. Further, 950 g of needle-shaped wood chips with a moisture content of 5.0% were preheated to 60°C, and 159 g of the organic polyisocyanate aqueous dispersion was uniformly sprayed onto the chips.
After being left for 30 minutes after application, particle board was produced in the same manner. The physical property measurement results of the obtained particle board are shown in Table 1.
The physical properties were also good when heated to . Comparative Example 200 parts of water-dispersible MDI obtained in Reference Example was added to 300 parts of water to obtain an organic polyisocyanate water dispersion.
The obtained organic polyisocyanate aqueous dispersion has a viscosity as shown below and does not exhibit thixotropic properties. Liquid temperature Rotation speed Viscosity measurement result 25°C 60RPM 0.5 poise 25°C 6RPM 0.5 poise Park takele board was manufactured using the obtained organic polyisocyanate aqueous dispersion in the same manner as in the example. The results of measuring the physical properties of the obtained particle board are shown in Table 1. The physical properties were relatively good at room temperature, but the physical properties were poor when heated to 60°C. 【table】

Claims (1)

[Scope of Claims] 1. An organic polyisocyanate compound dispersion containing xanthan gum and an isocyanate compound, characterized in that water or a mixture of a water-soluble organic solvent and water is used as a dispersion medium. 2. The organic polyisocyanate compound dispersion according to claim 1, wherein a reaction and/or mixture of an organic polyisocyanate and a nonionic surfactant is used as the organic polyisocyanate compound. 3. The organic polyisocyanate compound dispersion according to claim 1, wherein the nonionic surfactant is a monofunctional alkoxypolyalkylene glycol.