JPH0436845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims at converting a compound containing two or more epoxy groups in the molecule into a carboxyl group-containing esterified wood piece, which is obtained by adding a dibasic acid anhydride to the hydroxyl group in the wood. The present invention relates to a method for producing chemically modified wood pieces for molding, characterized in that the reaction is carried out in an equivalent ratio of groups: epoxy groups in the range of 1.0:0.3 to 1.5.

Fossil resources such as oil and coal are currently used in large quantities as industrial raw materials, but their reserves are limited and there are concerns about their future prospects. On the other hand, wood is a renewable resource and has been used in various fields. However, the effective use of unused wood such as small-diameter trees and thinned wood has not progressed much, and even more effective methods have been developed for the use of small pieces of wood, which are produced as industrial waste in industries that use wood. The current situation is that development is desired.

One of the conventional methods of using these materials is to mix small pieces of wood, especially wood flour, into plastics such as thermoplastic resins and thermosetting resins and use them as fillers and extenders. well known. However, in such applications, the wood flour is physically mixed with these resins and is merely incorporated therein in a dispersed state. Additionally, as the amount of wood flour added to the resin increases, the number of hydroxyl groups in the wood that have the ability to adsorb moisture increases, resulting in poor dimensional stability due to water absorption and moisture absorption of the resulting plastic molded product. A trend can be seen. Therefore, there was a limit to the amount of wood flour that could be mixed into plastics as a filler or extender.

On the other hand, a method of acetylating wood flour with acetic anhydride or the like has been known for the purpose of improving the water absorption and dimensional stability of wood flour due to moisture absorption. Also,
A known method is to esterify wood flour with a higher fatty acid such as lauric acid in order to impart thermoplasticity to the wood flour. However, since the esterified wood flour obtained by such a known method does not have crosslinking properties, an adhesive has sometimes been used when it is used for molding. Further, even if a plasticized sheet was produced by plasticizing the esterified wood flour by hot pressing, the mechanical strength was weak.

In addition, the present inventors first reacted a dibasic acid anhydride to a small piece of wood to esterify the hydroxyl group in the wood, thereby obtaining an esterified wood piece having a carboxyl group in the side chain. It has also been found that the resulting esterified wood chips can be easily plasticized by hot pressure. However, such carboxyl group-containing esterified wood chips are unstable to water and moisture at high temperatures, and if left in high temperature and high humidity (e.g. 40℃, 95%RH) for a long time,
There was a drawback that the ester bond was partially cleaved by hydrolysis. Further, even if a plasticized sheet was prepared by plasticizing small pieces of carboxyl group-containing esterified wood using heat and pressure in the same manner as described above, the resulting plasticized sheet had poor water resistance and other mechanical strengths.

In view of the above-mentioned circumstances, the present inventors have conducted intensive research and found that esterified wood particles containing carboxyl groups, in which dibasic acid anhydrides are added to the hydroxyl groups in the wood, have two or more molecules in the molecule. By reacting a compound containing an epoxy group with an equivalent ratio of carboxyl group to epoxy group in the range of 1.0:0.3 to 1.5, it has crosslinking properties and depending on the composition, excellent thermoplastic properties are imparted. It was discovered that chemically modified wood pieces for molding can be obtained, leading to the present invention.

That is, the present invention uses a carboxyl group-containing esterified wood piece obtained by adding a dibasic acid anhydride to the hydroxyl group in the wood. By reacting at a ratio of 1.0:0.3 to 1.5, the carboxyl groups of the esterified wood pieces undergo an addition esterification reaction with the epoxy groups in the epoxy compound, and the epoxy compound is added to the esterified wood pieces. A method for producing bonded, moldable, chemically modified wood pieces is provided.

The chemically modified wood pieces for molding obtained by the production method of the present invention have great industrial value and can be used under high temperature It is also possible to provide molded products having excellent properties that are stable against water and moisture.

The carboxyl group-containing esterified wood chips used in the present invention are made by reacting the wood chips with a dibasic acid anhydride to esterify the hydroxyl groups in chemical components such as cellulose, hemicellulose, and lignin contained in the wood composition. By doing so, carboxyl groups are chemically introduced into small pieces of wood.

Types of small pieces of wood include wood chips, wood fibers, finely divided wood powder, etc., and there are no particular restrictions on the raw wood or tree species. For example, red pine, cedar, cypress,
Birch, radiata pine, lauan, etc. are used.

In addition, dibasic acid anhydrides are dicarboxylic acid anhydrides, specifically maleic anhydride, succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride,
Examples include tetrapromphthalic anhydride, hexahydrophthalic anhydride, 3.6-dichlorophthalic anhydride, 4.5-dichlorophthalic anhydride, and itaconic anhydride.
Particularly preferred are maleic anhydride, succinic anhydride, phthalic anhydride, etc., which are industrially advantageous and inexpensive. Although the esterification reaction between the wood chips and the dibasic acid anhydride proceeds satisfactorily even in the absence of a catalyst, a basic catalyst such as sodium carbonate, dimethylbenzylamine, or pyridine may be used to accelerate the reaction. Further, the esterification reaction may be carried out in a solvent such as methylformamide or dimethyl sulfoxide. In addition, by adding the dibasic acid anhydride directly to a small piece of wood in the absence of a solvent and heating and stirring at a reaction temperature of 60°C or higher, the esterification reaction by addition proceeds smoothly.
Dibasic acid anhydride can be easily added to wood chips to obtain carboxyl group-containing esterified wood chips with various addition rates. In the above-mentioned esterification reaction in a solvent or without a solvent, the amount of dibasic acid anhydride added is preferably 5 to 50% per dry wood piece.
-200% by weight, more preferably 10-80% by weight. The addition rate of dibasic acid anhydride to the carboxyl group-containing esterified wood chips is preferably 5 to 120% by weight, more preferably 10% by weight based on the dry wood chips.
~70% by weight. After the reaction, the reaction product is washed and dried to obtain carboxyl group-containing esterified wood pieces used in the present invention. Further, when the amount of unreacted acid anhydride is small, the reaction product may be used as it is as a carboxyl group-containing esterified wood piece used in the present invention without washing after the reaction. The presence of this small amount of acid anhydride does not cause any disadvantage in the practice of the invention.

Examples of compounds containing two or more epoxy groups in the molecule used in the present invention include bisphenol type epoxy compounds obtained from bisphenol A and epichlorohydrin, nopolak type epoxy compounds obtained from phenolic resin and epichlorohydrin, and halogenated Halogenated epoxy compounds obtained from bisphenol A and epichlorohydrin, polyalkylene ether type epoxy compounds obtained from polyalkylene glycol and epichlorohydrin, polybutadiene type epoxy compounds obtained by epoxidizing the double bond portion of polybutadiene with peracetic acid, etc., and other diisocyanates. and epoxy compounds obtained from glycidol,
Examples include copolymers of vinyl compounds and glycidyl acrylate or methacrylate. Particularly preferred are bisphenol type epoxy compounds that are industrially produced in large quantities and available at low cost.

The amount of these epoxy compounds used is such that the amount of epoxy groups is 0.3 to 1.5 equivalents per equivalent of carboxyl group in the esterified wood chips. The amount is preferably 0.8 to 1.2 equivalents. If the amount of epoxy groups is less than 0.3 equivalent, the amount of unreacted esterified wood pieces becomes too large, and the resulting chemically modified wood pieces have a high acid value, which is not preferable. Further, if the amount exceeds 1.5 equivalents, not only unreacted epoxy compounds remain in the chemically modified wood pieces, but also it is economically expensive, which is not preferable. In addition, if unreacted dibasic acid anhydride exists in the esterified wood chips, an epoxy compound may be added to the above so that the epoxy group has the same amount as the anhydride group of the dibasic acid anhydride. preferable. In this case, a reaction between the acid anhydride and the epoxy compound also occurs as a side reaction, and this reaction product coexists in the chemically modified wood pieces for molding obtained in the present invention.
It does not have any negative effect on the final molded product.

Next, the manufacturing method of the present invention will be explained step by step. First, it is preferable to dry the small pieces of wood using a vacuum dryer, hot air dryer, etc. to remove moisture to a wood moisture content of 5% or less before use. Next, the production of carboxyl group-containing esterified wood pieces in which a dibasic acid anhydride is added to the hydroxyl groups in the wood is as described above, and in this way, the wood pieces are subjected to an addition esterification reaction with a dibasic acid anhydride. After that, generally
The reaction product is washed with acetone, water, etc. and dried. The obtained esterified wood pieces undergo a ring-opening esterification reaction between the hydroxyl groups in the wood and the dibasic acid anhydride, and the dibasic acid anhydride is added to the wood pieces.
It is clearly recognized from the infrared absorption spectrum analysis that a carboxyl group has been introduced into the side chain. These esterified wood pieces are used as carboxyl group-containing esterified wood pieces used in the present invention. Further, as described above, when the amount of unreacted dibasic acid anhydride is small, the reaction product may be used as it is as the esterified wood pieces used in the present invention without being washed.

Next, the above carboxyl group-containing esterified wood pieces are reacted with a compound containing two or more epoxy groups in the molecule at an equivalent ratio of carboxyl group:epoxy group of 1.0:0.3 to 1.5. . The reaction method is not particularly limited. However, since a long time is required when the reaction is carried out at a low temperature, a high temperature reaction is generally preferred. Here, heating and stirring in the reaction vessel will be described. In this case, the carboxyl group-containing esterified wood pieces and the above-mentioned epoxy compound are added to a reaction vessel equipped with a stirrer, and the mixture is heated and stirred at a predetermined temperature. As the epoxy compound, the above-mentioned bisphenol type epoxy compound is preferred. As the molecular weight increases, the crosslinking density decreases when molded, so it is usually 200~
It is preferable to have an average molecular weight of about 2000, and more preferably a liquid type. In some cases, as a diluent, a solvent that does not have reactivity with the epoxy compound, such as xylene, dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, etc., may be appropriately blended with the epoxy compound to dissolve it. and then added to the esterified wood chips. Further, although the addition esterification reaction between the esterified wood chips and the epoxy compound proceeds satisfactorily even without a catalyst, a basic catalyst such as sodium carbonate or dimethylbenzylamine may be used to accelerate the reaction. The reaction temperature varies depending on the type of epoxy compound, but is preferably in the range of 80°C to 200°C. The reaction time is preferably 1 to 10 hours.

As the reaction time progresses, the carboxyl groups of the esterified wood chips and the epoxy groups of the epoxy compound undergo an esterification reaction and are additionally bonded. It is preferable to stop the reaction at the stage where the carboxyl group and the epoxy group are partially bonded. When this chemically modified wood piece for molding, to which an epoxy compound is partially added and bonded, is easily plasticized when hot-press molded,
In addition, the crosslinking reaction proceeds simultaneously with the plasticization or after the plasticization, making it possible to provide a hard and strong wood molded product. However, in the present invention, it is necessary to carry out the reaction at least to the extent that no unreacted free epoxy compound is present in the system. This is because if there is a large amount of unreacted free epoxy compound, it will be removed from the system when high pressure is applied during hot press molding, which is uneconomical.

The chemically modified wood pieces for molding of the present invention are obtained in the manner described above, but depending on the case, the reaction product may be purified by washing with acetone or the like.

As mentioned above, the chemically modified wood pieces for molding obtained by the production method of the plate are obtained by adding the epoxy group of an epoxy compound to the side chain carboxyl group in the wood pieces, and have crosslinking properties. This makes it possible to provide molded products with excellent properties that are stable against water and humidity at high temperatures.

In addition, the chemically modified wood pieces for molding obtained by the production method of the present invention are mainly made from wood pieces produced as industrial waste in the wood industry, and have the characteristics of light weight and excellent workability of wood. It is possible to give molded articles, and the molded articles obtained by heat-pressing the chemically modified wood pieces for molding are suitable as materials for industrial parts in many fields.

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

Reference Example 1 15.0 parts of dried red pine wood powder (moisture content 5% or less) passed through a 24-mesh sieve, 60.0 parts of succinic anhydride, and 0.32 parts of sodium carbonate as a catalyst were added to a reaction vessel and stirred at 110°C for 6 hours. A carboxyl group-containing esterified wood flour (hereinafter referred to as esterified wood flour) was obtained by the following reaction. The addition rate of succinic anhydride added to the wood flour of this esterified wood flour was 46.7% by weight based on the wood flour.

Example 1 To 100 parts of the esterified wood flour obtained in Reference Example 1, EPOMIK R139 manufactured by Mitsui Petrochemical Epoxy Co., Ltd., diglycidyl ether of bisphenol A (hereinafter referred to as diglycidyl ether of bisphenol A) having an epoxy equivalent of 180 to 190 was added. (referred to as ether) was added to a reaction vessel and reacted at 140° C. for 6 hours with stirring to obtain chemically modified wood flour for molding. Further, a portion of the powdered reaction product was taken out, washed with acetone using a Soxhlet extractor, and then dried. After that, when we measured the addition rate of diglycidyl ether of bisphenol A added to the esterified wood flour of chemically modified wood flour for molding, we found that
It was 35.6% by weight.

Application example 1 When the chemically modified wood powder for molding obtained in Example 1 was subjected to hot pressure molding under the conditions of 180°C, 500 kg/cm ² and 60 minutes using a hot press, the surface was smooth with a thickness of 0.6 mm. A reddish-brown translucent plasticized board with excellent properties was obtained. This plasticized board was tough and hard, and showed no resistance in high-temperature, high-humidity tests (after placing the test piece in 40°C and 95% RH for 3 days, drying it at 80°C and observing the surface of the test piece). There was no change.

Comparative Example 1 When the esterified wood flour obtained in Reference Example 1 was subjected to hot pressure molding at 180°C, 500 kg/cm ² for 10 minutes using a hot press, a brown translucent product with a thickness of 0.6 mm was formed. A plasticized board was obtained. This plasticized board was soft and had low strength, and white powder was observed on the board surface even in high temperature and high humidity tests, and water resistance was low.

Reference example 2 15.0 parts of dried red pine wood powder (moisture content 5% or less) passed through a 24 mesh sieve, 60.0 parts of maleic anhydride,
0.32 parts of sodium carbonate as a catalyst was added to the reaction vessel, and the mixture was reacted at 120°C for 6 hours with stirring to obtain esterified wood flour. The addition rate of maleic anhydride added to the wood flour of this esterified wood flour was 50.1% by weight based on the wood flour.

Example 2 45 parts of diglycidyl ether of bisphenol A was added to 100 parts of the esterified wood flour obtained in Reference Example 2 in a reaction vessel, and the mixture was reacted with stirring at 140°C for 6 hours to produce chemically modified wood for molding. Got the powder. Since this reaction product was in a hard solid state, it was ground in a grinder.

Application example 2 When the chemically modified wood powder for molding obtained in Example 2 was subjected to hot pressure molding at 180°C, 500 kg/cm ² and 40 minutes using a hot press, it was found to have a thickness of 0.6 mm and a smooth surface. A glossy black-brown board with excellent properties was obtained. This board is strong and hard, and did not change at all during high temperature and high humidity tests.

Comparative Example 2 The esterified wood flour obtained in Reference Example 2 was subjected to hot pressure molding at 180°C, 500 kg/cm ² for 10 minutes using a hot press, and a reddish-brown translucent product with a thickness of 0.6 mm was obtained. A plasticized board was obtained. This plasticized board was soft and had low strength, and even in a high temperature and high humidity test, some white powder was observed on the surface of the board, indicating that it had low water resistance.

Claims (1)

[Claims] 1. A compound containing two or more epoxy groups in the molecule is added to a carboxyl group-containing esterified wood piece obtained by adding a dibasic acid anhydride to the hydroxyl group in the wood at an equivalent ratio of carboxyl group:epoxy group of 1.0:0.3~
A method for producing chemically modified wood pieces for molding, characterized in that the reaction is carried out in a range of 1.5.