JPS5832807A - Modifying method of woody material - Google Patents

Abstract

PURPOSE:To obtain a woody material having improved thermoplasticity causing the melting under heating, by treating the woody material with a reactant, e.g. an esterifying agent, grafting the treated woody material, making the woody material amorphous, swelling the material, and impregnating the woody material with a polymerizable substance. CONSTITUTION:A woody material is treated with a reactant reactive with the hydroxyl groups in the woody material, e.g. an esterifying agent or etherifying agent. A polymerizable substance, e.g. monomer, oligomer or prepolymer of a vinyl compound, is grafted onto the treated woody material to modify the woody material. The graft copolymerization is carried out by the conventional method, e.g. impregnating a radical polymerization catalyst, e.g. hydrogen peroxide or benzoyl peroxide, and the polymerizable substance into the woody material, and radically polymerizing the polymerizable substance. The modified woody material can be molded into an optional shape by applying heat and pressure thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying a wood material, which comprises chemically modifying hydroxyl groups in a wood component and then subjecting the wood material to a graft copolymerization treatment.

Wood materials lack thermoplasticity and cannot be easily deformed or densified by applying heat or heat and pressure at the same time, and their moldability is significantly inferior to that of general thermoplastic resins. Furthermore, wood materials have the disadvantage that they become carbonized when molded under severe heating conditions, and their tissue structure is damaged under severe pressurized conditions.

On the other hand, it has been known for a long time that physical properties such as dimensional stability of wood materials can be improved by acetylating or graft copolymerizing cellulose, which is the main component of wood materials.

In addition, the present inventors have discovered that it is possible to impart thermoplasticity to wood by treating it with an esterification agent or an etherification agent. When it comes to imparting, it is not easy except when higher fatty acids are used as the esterifying agent, when acetylation is performed using a trifluoroacetic acid-acetic acid system and then saponification by aging, or when acetylation is performed by a sulfuric acid catalyst method and then saponification by aging.

It has also been found that there is a problem with soil, and in the case of the sulfuric acid catalyst method, it is difficult to wash away the sulfuric acid after the reaction treatment.

As a result of further intensive studies, the inventors of the present invention found that after treating wood with a reactant that can react with the hydroxyl group in the wood components, such as an esterifying agent or an etherifying agent, the treated wood was graft copolymerized. By subjecting it to a chemical treatment, the reactant used is an esterifying agent or etherifying agent made of a highly practical lower fatty acid anhydride such as acetic anhydride. The present inventors have discovered that excellent thermoplastic properties can be easily imparted to wood materials even when using reactants that have been difficult to achieve, and have completed the present invention. That is, the present invention provides a wood material comprising: treating a wood material with a reactant capable of reacting with a hydroxyl group in the wood component; and then subjecting the treated wood material to a graft copolymerization treatment by reacting with a polymerizable substance. The present invention provides a method for modifying materials.

The method of the present invention is divided into a) a step of treating the wood material with a reactant (first step), and b) a step of graft copolymerizing the thus treated wood material (second step), which are detailed below. Explain.

In the first step, the wood material is brought into contact with the reactant by an appropriate means to chemically modify the hydroxyl groups of the wood components, particularly cellulose, and to amorphize the crystal structure of the cellulose.

Wood materials that can be used in the present invention may be in the form of powder particles, fibers, sheets, plates, columns, etc., but wood materials with thick shapes such as plates and columns are mainly modified on their surfaces. Often used for this purpose. Note that in this specification, the term "woody material" includes not only natural wood but also processed wood products such as plywood, laminated wood, fiberboard, and paperboard, and solidified plant materials other than wood.

As mentioned above, the term "reactant" refers to a substance that chemically reacts with the hydroxyl groups of wood components, particularly cellulose, and representative examples thereof include esterifying agents and etherifying agents.

Examples of esterification agents include organic acid anhydrides and hydrides (e.g. acetic acid,
acid anhydrides such as propionic acid, butyric acid), organic acid halides (e.g. acid halides such as propionic acid, lauric acid, stearic acid and methacrylic acid);
in particular acid chlorides), and mixtures of organic acid anhydrides and fatty acids (for example mixtures of trifluoroacetic anhydride or chloroacetic anhydride with acetic acid, propionic acid, caproic acid or lauric acid, etc.). These esterifying agents can be used alone or in combination of two or more. In particular, in the present invention, anhydrides and halides of lower fatty acids such as acetic acid and propionic acid are practically preferred in view of economical efficiency.

A catalyst for promoting the reaction with the wood component and/or a solvent for promoting the penetration of the esterifying agent into the wood cell membrane can be added to the esterifying agent. Such catalysts include perchloric acid, urea-ammonium sulfate,
Examples of solvents include acetic acid, benzene, toluene, dimethylformamide, dinitrogen tetroxide-dimethylformamide, and the like, and may be used as a mixture of two or more of each.

Instead of or in addition to being added to the esterifying agent, these catalysts and/or solvents may be impregnated in advance into the wood material before being treated with the esterifying agent.

Next, examples of the etherification agent include 1,2-epoxides such as ethylene oxide and propylene oxide, alkyl halides such as methyl chloride and ethyl chloride, aromatic halides such as benzyl chloride, dialkyl sulfates such as dimethyl sulfate, α-halogen acids such as monochloroacetic acid, vinyl compounds activated with negative groups such as vinyl cyanide, aldehydes such as formaldehyde, and the like can be used.

In the case of an etherification agent, as in the case of an esterification agent, a catalyst (for example, an alkaline catalyst such as sulfur hydroxide) is used.
or a solvent (for example, a solvent similar to that used in the case of an esterification agent) can be added as appropriate, or the wood material can be pre-impregnated with these before being treated with the etherification agent. In the case of catalysts, the latter is particularly preferred.

Examples of reactants that can react with hydroxyl groups include isocyanates (for example, methyl isocyanate, ethyl isocyanate, etc.) in addition to the esterifying agents and etherifying agents listed below.

The reactant may be brought into contact with the wood material by, for example, immersing the wood material in the reactant, or by vaporizing the reactant and exposing the wood material to this. Further, such a method can be carried out under reduced pressure, under increased pressure, or by a reduced pressure method to promote impregnation of the reactant into the wood material.

Through chemical treatment with such reactants, wood components,
In particular, when the hydroxyl groups of cellulose undergo chemical modification such as esterification and etherification, the crystalline structure of cellulose becomes amorphous, and thus a wood material in a swollen state is obtained.

At this time, the hydroxyl groups of hemicellulose and lignin, which are the main components of wood along with cellulose, may also undergo similar chemical changes, and in this case, the bonds between the wood components become weaker, and the degree of swelling of the wood increases. It becomes noticeable.

The treated wood material obtained in the first step is subjected to the second step of graft copolymerization treatment.

Graft copolymerization treatment involves immersing the wood material in a polymerizable substance, exposing it to a vaporized polymerizable substance, or applying a polymerizable substance to the wood material, and then graft copolymerizing it by an appropriate method. Consists of things.

As the polymerizable substance, monomers, oligomers, and prepolymers of vinyl compounds such as methyl methacrylate, styrene, acrylic acid, acrylonitrile, acrylamide, and butadiene can be used.

Graft copolymerization can be carried out according to conventional methods. That is, for example, a method of impregnating a wood material with a radical polymerization catalyst such as hydrogen peroxide, benzoyl peroxide, azobisisobutyronitrile, ammonium persulfate, potassium persulfate, etc. together with a polymerizable substance and carrying out radical 1° polymerization, similarly as 1. Methods include a method using a redox catalyst such as a cerium salt, and a method in which wood material is impregnated with a polymerizable substance and then irradiated with radiation such as gamma rays or electron beams, and any method may be used.

As mentioned above, the wood material obtained in the first stage treatment becomes amorphous,
Because it has been swollen, in this second stage of treatment,
The polymerizable substance is sufficiently and easily impregnated not only into voids such as conduits and tracheids but also into cells, and thus a highly uniform graft copolymer can be obtained. It should be noted that not all of the polymerizable substance impregnated into the wood material participates in the graft copolymerization, and some of it is considered to become a homopolymer and remain in the voids of the wood material, but this does not need to be particularly removed.

Rather, the presence of the homopolymer has the advantage of improving compatibility with the graft copolymerized wood component, and can often improve the physical properties of the final molded product as a composite.

The modified wood material thus obtained is treated with reactants such as esterification agents and etherification agents, whereby the glacial acid groups in its components are chemically modified and internal plasticization progresses. By being graft-copolymerized with a polymerizable substance, it is imparted with such remarkable thermoplasticity that it can easily be thermally melted.

Particularly when using as reactants acid anhydrides, anhydrous lower fatty acids such as propionic anhydride, and other substances that have high practicality but have conventionally been difficult to impart remarkable thermoplasticity to the extent of complete thermal melting. It is also possible to impart remarkable thermoplasticity to these materials by graft copolymerization.

Therefore, the wood material obtained by the method of the present invention can be used, for example, in the following manner by taking advantage of its high thermoplasticity.

When the method of the present invention is applied to granular or fibrous wood materials, it is easier to mold the wood material after modification or by applying heat and pressure to the wood material mixed with other synthetic resins. It can be formed into any shape by extrusion molding, injection molding, or other molding processes. Further, when applied to a sheet-like plate-like wooden material, it can be extremely easily formed into a curved or bent shape. Furthermore, when the method of the present invention is applied to the surface of a thick plate-like or columnar wood H, the surface can be formed into a dense material with excellent water resistance and abrasion resistance by heating and pressing it. can. Furthermore, desired physical properties can be imparted to these molded products by grafting vinyl polymers such as styrene onto the wood components and by the type and amount of the homopolymer remaining in the wood voids. By adjusting the pressurizing conditions, it is possible to adjust the heat softening state and heat melting state of the modified wood material, and form a molded product with a desired appearance quality without causing carbonization or damage.

Examples of the present invention are listed below.

[Example 1] 15 g of wood flour was pretreated by immersing it in 26.3 ml of glacial acetic acid for several hours, and then 62.2 ml of acetic anhydride was added to 36.3 ml of propionic anhydride. s tgl (molar ratio 7:3) to glacial acid 4
Add 8 tnl perchloric acid 0.19 rat and bring the solution temperature to 35°C.
The mixture was immersed for 6 hours to react, washed and dried to obtain acetyl-propionylated wood flour.

Put 5 g of this acetyl-propionylated wood flour into a reaction container, add 20 m/s of pyridine and 20 m/s of styrene, and then directly exchange nitrogen inside the container.
Simultaneous irradiation with 60r radiation was performed for 19 hours, and after the reaction was completed, the homopolymer was immersed in methanol to co-precipitate the homopolymer. The homopolymer of the obtained graft copolymerized wood flour 1 was removed by benzene extraction, and the apparent grafting rate was calculated to be 12% (the grafting efficiency was 35%).

Also, under the same conditions as in Section 2, the dose rate Q −IMrad/
Graft copolymerization treated wood flour 2 by changing only the C060r simultaneous irradiation time of hr to 1 hour, 24 hours, or 34 hours.
, 3.4 was obtained.

The apparent grafting rates of the graft copolymerization-treated wood flours 2 and 3.4 were 2%, 15%, and 18%, respectively.

Next, the graft copolymerized wood powder 1 obtained above
, 2, 3, 4, and the acetylpropionylated wood flour '5 obtained in the above operation (without graft copolymerization treatment) were subjected to pressure crab 3 using a thermomechanical testing machine (manufactured by Kanku Riko Co., Ltd.). Thermoplasticity was measured based on 9/cl and heating rate: IC/min. The results are shown in Figure 1 (thermo-mechanical behavior diagram).

In No. 11, the vertical axis shows the amount of depression deformation (Δ) due to thermal softening of the sample due to heating, and the horizontal axis shows the heating temperature (T).

As is clear from FIG. 1, acetyl-propionylated wood flour 5 undergoes thermal softening, but does not completely thermally fluidize even at temperatures of 3006 C or higher, whereas graft copolymerized wood flour 1, 2,: It was confirmed that, even at a small apparent grafting rate, Samples ', , and 4 exhibited complete thermal fluidity at approximately 300°C and were endowed with remarkable thermoplasticity accompanied by melting.

In addition, the obtained graft copolymerization treated wood flour 1,2°3.4
can reduce the heating temperature by applying strong pressure,
For example, by hot pressing at 150° C. and 100 KS'/cm, it was possible to suitably mold the wood flour into a sheet-like molded product.

' [Example 2] After pre-treating 15 pieces of wood flour under the same conditions as in Example 1,
Acetic anhydride 89.1 ml Glacial acetic acid 413 g 1 Perchloric acid 0,
It was immersed in a 19 ml mixed solution at a temperature of 35° C. for 6 hours to react, washed and dried to obtain acetylated wood flour.

Put 5 g of this acetylated wood flour into a reaction container and add 20 g of pyridine.
After adding tsl and 20 g of styrene and purging the inside of the container with iM nitrogen, simultaneous irradiation with C060r rays was performed for 10 hours at a dose rate of Q-IMrod.

The obtained graft copolymerization-treated wood flour 6 had an apparent grafting rate of 8% (grafting efficiency of 30%).

Example 1 This graft copolymerization treated wood flour 6 and the acetylated wood flour 7 obtained by the above operation (not subjected to graft copolymerization treatment) were tested in the thermomechanical testing machine described in Example 1. Thermoplasticity was measured under the same conditions as . The results are shown in FIG.

As is clear from Figure 2, acetylated wood flour 7 has a
It was confirmed that the graft copolymerized wood flour 1 showed complete thermal fluidity at approximately 300° C. and was endowed with remarkable thermoplasticity, whereas the wood flour 1 did not have complete thermal fluidity even at a temperature of 300° C.

[Example 3] 5 g of acetyl-propionylated wood flour obtained in Example 1
was placed in a reaction vessel, and 50 yttl of an aqueous solution containing 1 x 10-3 mol of FeSO4, 50 ml of an aqueous solution containing 10-2 mol of hydrogen peroxide, and 80 ytl of methyl methacrylate were added, and the reaction was carried out at 50°C for 4 hours. Ta.

The apparent grafting rate of the resulting graft copolymerized wood flour was 60% (grafting efficiency 22%). This graft copolymerized wood flour was also endowed with remarkable thermoplasticity that caused perfect thermal flow.

[Example 4] 5 g of the acetylated wood flour obtained in Example 2 was immersed in a 2% ammonium persulfate aqueous solution for 30 minutes, and then 50 g of methyl methacrylate and 50+/! of methanol were added. Add
The reaction was carried out at 60°C for 3 hours.

The apparent grafting rate of the resulting graft copolymerized wood flour was about 120%.

This graft copolymerization-treated wood flour also had significant thermoplasticity that resulted in perfect thermal flow.

[Brief explanation of the drawing]

Figures 1 and 2 show thermomechanical behavior diagrams before and after graft copolymerization treatment with acetyl-pro, respectively. 1.2, 3.4 and 6...Graft copolymerization treated wood flour with apparent graft ratios of 2%, 12%, 15%, 18% and 8%, respectively, 5 and 7...Graft Wood flour before copolymerization treatment.

Claims (3)

[Claims] (1) Modification of wood material comprising treating wood material with a reactant capable of reacting with hydroxyl groups in the wood component, and then reacting the treated wood material with a polymerizable substance and subjecting it to graft polymerization treatment. Method. (2) The method for modifying wood materials according to claim 1, wherein the reactant is an esterification agent or an etherification agent. (3) The method for modifying wood materials according to claim 1 or 2, wherein the polymerizable substance used in the graft polymerization treatment is a vinyl compound monomer, oligomer, or prepolymer.