JPH0515726B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a binder composition for a grindstone made of solid polyurethane that easily melts and reacts when heated to form a strong grindstone with excellent heat resistance. A polyurethane resin is obtained by reacting a compound having an active hydrogen group with an isocyanate group. Commercially, even if it is cured by other reaction methods that do not produce urethane bonds, it is sometimes called polyurethane when isocyanate is used as a curing agent, but in a narrow sense, it is cured by producing urethane bonds. It refers to a compound produced by the reaction of a compound with a hydroxyl group and an isocyanate group. In this case, the produced polyurethane resin strongly reflects the properties of the "hydroxyl group-containing compound" used. Polyurethane resins are generally used in liquid or solution form. There are only a few examples of thermoplastic resins, hot melt adhesives, powder coatings, etc. in which solids are softened or melted by heating. These raw materials include polyisocyanates, such as diphenylmethane diisocyanate, which are supplied in the form of lumps or flakes at room temperature, and even if they are liquid at room temperature, they can be easily solidified by blocking with phenols, secondary alcohols, etc. It can be supplied in bulk or powder form. On the other hand, as compounds having hydroxyl groups, polyester polyols, polyether polyols, etc. are usually used, but these are in liquid or wax form. If waxy,
If the melting point is high, it is possible to use it in a solid state, but the polyester polyol normally provided has a low melting point even in the form of a wax, making it unsuitable for use in the form of lumps, flakes, sheets, or powder. do not have. As described above, since there is no solid polyester that satisfies the storage stability (sintering, blocking) and excellent heat resistance, there has been a strong demand for improvement. The present invention provides a solid polyester polyol that has a high melting point, is stable in bulk or powder form, and is easy to handle.When combined with solid polyisocyanate, it can be heated and melted and reacted easily. The present invention relates to a method for producing a binder composition for a grindstone made of solid polyurethane that produces a tough and heat-resistant polyurethane resin. That is, general formula [] R=OH, (-OCH ₂ CH ₂ )-OH,

[Formula] A glycol mixture containing 50 mol% or more of the total glycol components, preferably 70 mol% or more of the glycol n, m = 1 to 5, and a polyester polyol consisting of a bifunctional or polyfunctional organic acid as a hydroxyl group-containing component. This is the gist of the present invention. General formula [] Since the six-membered heterocycle has excellent heat resistance, polyester polyols containing it and polyurethane resins produced from it also exhibit excellent heat resistance. These properties become more remarkable as the content of the heterocycle represented by the general formula [] increases. The glycol represented by the general formula [] accounts for 50 mol% of the total glycol components.
This is the reason why the content is preferably 70 mol% or more. If the glycol represented by the general formula [] is less than 50 mol% of the total glycol components, the heat resistance will not be sufficient. In the general formula [], R is OH, (-OCH ₂ CH ₂
) _o --OH,

[Formula] may be the same or different, but the smaller n or m is 3 or less, the better the heat resistance. When n or m is larger than 5, heat resistance decreases, but compatibility with isocyanates and other resins and solubility in solvents tend to improve. A suitable value for n or m should be adopted depending on the purpose. Regarding heat resistance, it is desirable that n and m be 5 or less. Moreover, the larger n or m becomes, the more sticky the polyester polyol becomes and the more difficult it becomes to powder it. When used in powder form, it is desirable to keep n or m to 3 or less. There are no particular restrictions on the glycol used in combination with the substance of general formula [], but examples include ethylene glycol, diethylene glycol, propylene glycol, 1,3-butylene glycol,
Examples include 1,4-butylene glycol, 1,6-hexane glycol, neopentyl glycol, and the like. Examples of organic acids include adipic acid, maleic acid, fumaric acid, phthalic anhydride, terethalic acid, isophthalic acid, trimellitic acid, pyromellitic anhydride, and alkylates thereof. The polyisocyanate to be combined with the above-mentioned polyester polyol having the general formula [] in its molecular structure may be difunctional or more and solid at room temperature.The present invention does not limit this, but an example is diphenylmethane diisocyanate (hereinafter referred to as MDI). ), MDI
and/or toluene diisocyanate (hereinafter referred to as TDI)
There are dimers, trimers, and blocks of various polyisocyanates. Polycysocyanates used for the preparation of block bodies include TDI, MDI, polyphenylmethane polyisocyanate, hexamethylene diisocyanate (hereinafter abbreviated as HDI), isophorone diisocyanate,
Examples include tolidine diisocyanate, xylylene diisocyanate, 1,5-nastyrene diisocyanate, hydrogenated diphenylmethane diisocyanate, lysine diisocyanate, and the like. Masking agents used for block bodies include phenols such as carbolic acid, cresylic acid, and xylenolic acid;
Propyl alcohol, 2-butyl alcohol, 2
- Secondary alcohols such as aluminum alcohol, ε-caprolactam, MEK oxime, etc. These exemplified compounds are not intended to limit the scope of the present invention. The molar ratio of NCO/OH in the combination of these solid polyisocyanates and polyester polyols is preferably 1/1 to 1.2/1. In this case, if the molar ratio is less than 1/1, the resin It begins to show a tendency to become brittle. If the ratio is greater than 1.2/1, the resin may remain sticky or foaming may occur. When combining a polyester polyol having the general formula [ ] in its molecular structure with a solid polyisocyanate, the common method of mixing is to mix separately powdered powders. In the case of blocked isocyanate, After melting and mixing at a temperature below the dissociation temperature, the materials can be formed into a sheet, a lump, or a powder. The binder composition for grinding wheels made of solid polyurethane thus obtained is solid and has particularly excellent storage stability and resin heat resistance, and is widely used as a binder for powder coatings, adhesives, inorganic materials, etc. It can be used for. The present invention will be further explained in detail with reference to Examples. Example 1 1.8 mol of spiroglycol, 0.2 mol of neopentyl glycol, and 1 mol of phthalic anhydride were esterified by a conventional method to obtain a pale yellow solid. This is mixed in a powder frame with Millionate MT-F (MDI flakes manufactured by Nippon Polyurethane Industries) so that NCO mole/OH mole = 1.05. This mixed powder was mixed with carborundum at a weight ratio of 20%, and heated at 200° C. for 20 minutes while pressing at 20 kg/cm ² to obtain a grindstone. It has a lifespan 1.5 times longer than that of a grinding wheel with a normal phenolic resin binder. Comparative Example 1 A mixture of 0.8 mol of spiroglycol, 1.2 mol of ethylene glycol, and 1 mol of adipic acid was placed in a four-necked flask and esterified at room temperature. A pale yellow waxy substance was obtained, but it could not be powdered. Comparative Example 2 The pale yellow glassy solid polyester obtained in Example 1 and isophorone diisocyanate, which is liquid at room temperature, are mixed so that NCO mol/OH mol=1.05. The resulting mixture partially gelled, became a very heterogeneous solid, and had storage stability problems such as reaction between isocyanate groups and active hydrogen groups in the polyester.

Claims (1)

[Claims] 1. General formula However, R=OH, (-OCH ₂ CH ₂ ) _o --OH,
[Formula] A solid polyester polyol obtained from a glycol mixture containing 50 mol % or more of the total glycol components and an organic acid, with glycol n, m = 1 to 5, and a polyisocyanate or block polyester polyester polyol that is solid at room temperature with two or more functional groups. A method for producing a binder composition for a grindstone comprising solid polyurethane, which comprises mixing an isocyanate.