JPH0513041B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a method for producing a wood-plastic composite material having excellent dimensional stability, hardness, abrasion resistance, mechanical strength, durability, etc. (Prior Art) This type of wood-plastic composite material is generally produced by impregnating wood with synthetic resin monomers or oligomers and polymerizing the impregnated wood. As specific manufacturing methods, the heated air bath method (oven method) and the hot plate hot press method (hot press method) have been adopted, and the latter hot plate hot press method in particular uses conduction heat. It is widely used because it uses radiant heat, has relatively good thermal efficiency, and has the advantage of suppressing warping of wood by pressing. (Problems to be Solved by the Invention) However, the above hot plate heat pressing method also has the following problems. a) Since large-scale hot press equipment is required, the initial capital investment is large. b High-temperature heating (approximately 100 to 130°C) is required for polymerization, resulting in high energy costs. c. If the wood is thin, it can be polymerized in a short time, but if it is thick, it will take a long time for the inside to reach the polymerizable temperature. Furthermore, because of this, it is not possible to process materials of different thicknesses at the same time, resulting in poor production efficiency. d If the moisture content of wood is high, cracks and deformation may occur due to expansion due to vaporized moisture during heating and volume changes due to changes in moisture content before and after heating. e Due to the expansion of the air in the wood and the impregnating ingredients due to heating, the impregnating ingredients may leak from the wood end surface and adhere as a polymerized and cured product, which requires a great deal of effort to remove and may cause loss of monomers or oligomers. big. f Uncured monomer vapor is released during heating, which poses a major problem in terms of work hygiene and also poses a great risk of fire. This invention was made to solve the above-mentioned conventional problems, and is a wood-plastic composite that has low production and equipment costs, does not cause cracking or deformation during manufacturing, and has excellent workability and safety. The purpose is to provide a method for manufacturing materials. (Means for Solving the Problems) For the above-mentioned purpose, the present invention provides a component for impregnating wood with a composition that can be polymerized at medium to low temperatures, and separates this into two liquids that do not polymerize before impregnation. In this method, two-stage impregnation is performed to polymerize the material. That is, in this invention, after impregnating wood with either a polymerization initiator or a polymerization accelerator,
Impregnate the other component with vinyl monomer and
A method for producing a wood-plastic composite material characterized by polymerizing at a temperature below ℃, and storing wood in an airtight container and degassing the inside of the container,
A solution containing either a polymerization initiator or a polymerization accelerator was injected into the container from the first storage tank to immerse the wood, and then the excess solution was returned to the first storage tank to reduce the pressure inside the container again. Afterwards, a liquid containing the other component and a vinyl monomer or oligomer is injected into the container from the second storage tank, and the wood is immersed at a temperature of 60°C or less, and then the excess liquid is returned to the second storage tank for further soaking. This method of producing a wood-plastic composite material is characterized in that the wood is left at the above temperature for a required period of time, and then the wood is taken out from the container. (Specific Structure of the Invention) In the present invention, the components to be impregnated into wood are at least a three-component system consisting of a vinyl monomer or oligomer, a polymerization initiator, and a polymerization accelerator. That is, when using a two-component system of a vinyl monomer or oligomer and a polymerization initiator as the impregnating component, high-temperature heating is required for polymerization as described above, but when using a three-component system that includes a polymerization accelerator. Therefore, polymerization can be carried out at medium to low temperatures below 60°C, usually at room temperature (about 20°C). Therefore, according to the present invention, all of the various problems caused by high temperature heating during polymerization in the conventional methods described above are solved. In addition, in this invention, either the polymerization initiator or the polymerization accelerator is a two-component type separated from the vinyl monomer or oligomer, and after this separated component is first impregnated into the wood, the other component is mixed with the vinyl monomer or oligomer. A two-stage impregnation is performed in which monomers or oligomers are impregnated. In other words, if the three components mentioned above are present at the same time, polymerization will proceed immediately, but by employing two-stage impregnation, it becomes possible to recover and reuse the surplus components subjected to impregnation in an almost unreacted state, and the raw material This makes it possible to maximize the utilization rate and reduce costs. Further, by using the two-component type, it is possible to avoid the possibility that polymerization progresses during storage and the product becomes unusable. In this invention, the vinyl monomer that is the main agent for polymerization includes, for example, lower alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate;
Various monomers containing polymerizable vinyl groups such as styrene, vinyl acetate, and acrylonitrile can be used, and two or more of these monomers may be used in combination. Moreover, oligoester acrylates are suitable as oligomers, and these may be used in combination with the above monomers. Examples of the polymerization initiator include ketone peroxides such as methyl ethyl ketone peroxide, hydroperoxides such as t-butyl hydroperoxide, organic peroxides such as diacyl peroxides such as benzoyl peroxide, or organic peroxides such as azoisobutyronitrile. Including azo compounds, any of those conventionally known as polymerization initiators for vinyl monomers or oligomers can be used, and two or more of these may be used in combination. The amount used is preferably about 0.2 to 1.0% by weight based on the vinyl monomer or oligomer. As the polymerization accelerator, any known chelating agent that acts on the polymerization initiator can be used, typical examples of which include cobalt naphthenate, dimethylaniline, organic vanadium compounds, ascorbic acid, and the like. The amount used is preferably about 0.5 to 2.0% by weight based on the vinyl monomer or oligomer. In addition, in the method of this invention, either the polymerization initiator or the polymerization accelerator used in the first step of impregnation is used in the form of a solution dissolved in a solvent such as methanol, and after impregnating the wood, it is used as a solution. It is best to volatilize the solvent. Also, after this solvent volatilization, the second
It is desirable to deaerate the wood using vacuum suction or the like in order to sufficiently spread the impregnation of the steps into the interior of the wood. FIG. 1 shows a preferred apparatus configuration for use in the method of this invention. In the figure, 1 is a closed type cylindrical container arranged horizontally, 2 is a vacuum pump, 3 is a first storage tank, and 4 is a second storage tank, and both storage tanks 3 and 4 are arranged below the container 1. An intake pipe 5a from the vacuum pump 2 is connected to the upper part of the container 1 via a valve 6a, and a liquid guide pipe 7b is connected to the lower part of the container 1 from the lower parts of both storage tanks 3 and 4 through valves 6b and 6c, respectively. ，
A liquid guiding pipe 7a is connected to the vacuum pump 7c, and the vacuum pump 2 and the upper parts of both storage tanks 3 and 4 are connected to each other via intake pipes 5b and 5c via valves 6d and 6e, respectively. Next, a method for manufacturing a wood-plastic composite material using the apparatus shown in FIG. 1 will be explained. First, a solution containing either a polymerization initiator or a polymerization accelerator is placed in the first storage tank 3, and a mixed solution containing the other component and a vinyl monomer or oligomer is placed in the second storage tank 4. Then, after storing the wood that has been processed into the required dimensions and shape as a product in the container 1 and sealing the container 1, the valve 6a is opened and a vacuum pump is applied in order to fully apply the plastic composite to the inside of the wood. At step 2, the inside of the container 1 is vacuum-suctioned to remove the air inside the wood. Next, by opening the valve 6b, the first storage tank 3 is placed in the container 1 under reduced pressure.
After the solution is automatically introduced and the wood is immersed in it for a certain period of time, the valve 6a is closed to return the inside of the container 1 to normal pressure, and the valve 6d is opened to drain the first storage tank 3.
By reducing the pressure inside the container 1, all the excess solution in the container 1 is automatically refluxed into the first storage tank 3, and the valve 6
b is closed and then left to stand for a certain period of time to evaporate and evaporate the solvent component of the solution impregnated into the wood. As a result, the wood is impregnated with only the polymerization initiator or polymerization accelerator. Next, the valve 6a is opened again to reduce the pressure inside the container 1 for a certain period of time, and then the valve 6a is opened again.
c is opened to automatically introduce the mixed liquid from the second storage tank 4 into the container 1 under reduced pressure, and the wood is immersed in this for a certain period of time.Then, the valve 6a is closed to return the inside of the container 1 to normal pressure, and the valve 6a is closed. By opening 6e and reducing the pressure in the second storage tank 4, all the excess solution in the container 1 is automatically refluxed into the second storage tank 4, and then the container 1 is left to stand for a certain period of time. As a result, the vinyl monomer or oligomer impregnated into the wood is polymerized and hardened by the action of the polymerization initiator and polymerization accelerator. In addition,
At this time, if the outside temperature is very low or if it is necessary to particularly increase the polymerization rate, the inside of the container 1 may be heated to a temperature of up to 60°C. In this way, the wood taken out from inside the container 1 becomes a composite material in which the inside is impregnated with synthetic resin and hardened, and has excellent dimensional stability, abrasion resistance, and high hardness.
It has good mechanical strength and durability. Since high-temperature heating is not applied during polymerization, there is almost no dimensional change before and after impregnation polymerization, and by pre-processing the wood before treatment, the composite material taken out from container 1 can be directly coated with an undercoat or top coat on the surface. It can be made into a product by applying the required coating such as wood. Therefore, there is no need to perform difficult processing on the hard composite material. (Examples) Hereinafter, the present invention will be described in detail based on Examples. In addition, in the following, parts mean parts by weight. In addition, the processing in each example was performed at room temperature 20°C.
I went nearby. Example 1 Tangential direction 10mm, radial direction 70mm, fiber direction 130mm
Using Douglas fir wood with dimensions as a polymerization accelerator.
After being immersed in a methanol solution containing 1.0% by weight of ascorbic acid for 10 minutes under normal pressure, the methanol component was evaporated and diffused. Next, this Douglas fir material was placed in a desiccator and vacuum degassed for 20 minutes.
An impregnating solution prepared by adding 1 part of benzoyl peroxide as a polymerization initiator to a solution mixed in a ratio of 57 parts of tetraethylene glycol diphthalate, 29 parts of ennea ethylene glycol methacrylate, and 14 parts of trimethylolpropane trimethacrylate was introduced into the desiccator. The sample was impregnated under reduced pressure for 10 minutes, returned to normal pressure, left to stand for 10 minutes, and then taken out. The obtained wood-plastic composite material had a polymer retention rate of 16% as expressed by the following formula. Polymer retention rate (%) = Absolute dry weight of treated material - Absolute dry weight of untreated material / Absolute dry weight of untreated material x 100 When the above operation was repeated 8 times, no abnormality was observed in the residual impregnating solution. Composite materials of almost the same quality were obtained in both cases. Next, the obtained composite material was left at room temperature for 24 hours, and then a polyurethane sealer was applied as an undercoat and a vinylidene fluoride clearer was applied as an overcoat. Example 2 A spruce material measured in the same manner as in Example 1 was immersed in a methanol solution containing 0.5% by weight of dimethylaniline as a polymerization accelerator under normal pressure for 10 minutes, and then the methanol component was evaporated and diffused. Next, Example 1 was carried out using an impregnation liquid having the same composition as in Example 1.
A wood-plastic composite material was obtained by impregnation treatment in the same manner as above. The polymer retention rate of this composite material is 21%
It was hot. Note that when the above operation was repeated eight times, no abnormality was observed in the residual impregnating solution, and composite materials of substantially the same quality were obtained in all cases. Example 3 A Douglas fir wood measured in the same manner as in Example 1 was immersed in a methanol solution containing 0.5% by weight benzoyl peroxide as a polymerization initiator for 10 minutes under normal pressure, and then the methanol component was evaporated and diffused. Next, an impregnation treatment was carried out in the same manner as in Example 1 using an impregnating liquid in which 1 part of dimethylaniline was added as a polymerization accelerator in place of benzoyl peroxide in the impregnating liquid composition of Example 1 to obtain a wood-plastic composite material. Ta. The polymer retention rate of this composite material was 16%. Example 4 In the apparatus shown in FIG. 1, the inner diameter of the container 1 is
Use a tank with an internal length of 30 cm and 4 mm, and the first storage tank 3
1% by weight of ascorbic acid as a polymerization accelerator
A methanol solution was contained therein, and an impregnating liquid having the same composition as in Example 1 was also contained in the second storage tank 4. Then, inside container 1, 30 mm in the tangential direction, 80 mm in the radial direction, and 80 mm in the fiber direction.
After a spruce material having a size of 500 mm was housed and sealed, the inside of the container 1 was vacuum-suctioned at 60 Torr for 2 minutes to perform deaeration treatment. Next, the solution in the first storage tank 3 is introduced into the container 1 by operating the valve.
After the immersion treatment for a minute, the inside of the container 1 was returned to normal pressure, the excess residual liquid was refluxed into the first storage tank 3, and the methanol component was allowed to evaporate and diffuse for 10 minutes. Next, the inside of the container 1 was degassed by vacuum suction at 60 torr for 5 minutes, and then the impregnating liquid in the second storage tank 4 was introduced into the container 1, and after being immersed for 1 minute, the inside of the container 1 was returned to normal pressure. The excess residual liquid is refluxed into the second storage tank 4, and further
After leaving it for 10 minutes, it was taken out from container 1. The polymer retention rate of the obtained wood-plastic composite material was 5%. In addition, when the above operation was repeated 8 times, the second
No abnormality was observed in the impregnating liquid in the storage tank 4, and composite materials of almost the same quality were obtained in all cases. (Performance test) Next, the composite material obtained in Example 1 after surface painting, the composite material obtained in Example 2, and the Douglas fir material used in Example 1 were directly coated on the same surface as in Example 1. The anti-expansion ability (ASE) was measured after 6 months of outdoor exposure for the coated product (Reference Example 1), the product whose surface was also coated with antiseptic paint (Reference Example 2), and the product which was also untreated (Reference Example 3). ), anti-water absorption capacity (RWA), and total crack length were measured.
The results shown in Table 1 were obtained. In addition, the ASE, RWA, and total length of cracks were measured after a 600-hour accelerated weather test using a weather-ometer using a sunshine in-arc lamp, and the results shown in Table 2 were obtained.

[Table] ○ With treatment × Without treatment Total length of crack = Length of one crack
size x number of cracks

[Table] ○ With treatment × Without treatment Total length of crack = Length of one crack
x Number of cracks Furthermore, for the composite material of Example 1, the surface-coated Douglas fir material of Reference Example 1, and the untreated Douglas fir material of Reference Example 3, the degree of discoloration over time in the accelerated weather resistance test using the Weatherometer was measured using a color difference meter. The results of the measurements are shown in FIG. Furthermore, for the composite material of Example 2, the changes in RWA and ASE over time during the outdoor exposure are shown in FIG. Curve A in Figure 2 is Example 1, curve B is Reference Example 1, and curve C is Reference Example 3.
respectively. From the results in Table 1, Table 2 and Figures 2 and 3,
It can be seen that the wood-plastic composite material obtained by the method of this invention is extremely excellent in dimensional stability, mechanical strength, durability, etc. (Effects Unique to the Invention) According to the method for producing a wood-plastic composite material according to the present invention, after impregnating wood with one of the components of a polymerization initiator and a polymerization accelerator, the other component is impregnated with the other component. Since a two-stage impregnation process is performed in which vinyl monomers or oligomers are impregnated and polymerization is performed at medium to low temperatures, energy costs are significantly reduced and large-scale production is possible compared to conventional methods that require high-temperature heating for polymerization. This eliminates the need for additional heating equipment, lowers equipment costs, prevents leakage of impregnated components from the end surface of the wood, saves the effort of removing polymerized deposits from this leakage, and suppresses raw material loss. Since there is almost no change in rate, cracks and deformation are unlikely to occur, and there is no change in dimensions before and after the impregnation polymerization treatment, so it is possible to press cut the product, that is, to process the dimensions and shape into the final finished product before processing. . In addition, in the method of this invention, even if the thickness of the wood is different, the polymerization is completed in almost the same amount of time, so it is possible to process wood of different thickness at the same time, and production efficiency can be significantly improved. Furthermore, since there is almost no evaporation and scattering of the monomer, there is no problem in terms of work hygiene, there is little risk of fire or other dangers, and the handling is good.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of the configuration of the apparatus used in the method of the present invention, and Fig. 2 is a characteristic diagram showing the degree of discoloration over time of samples obtained in Examples and Reference Examples under a weather resistance test using a Weatherometer. , FIG. 3 is a characteristic diagram showing the changes over time in anti-swelling ability (ASE) and anti-water absorption ability (RWA) of the samples obtained in Examples. 1... Airtight container, 3... First storage tank, 4... Second storage tank.

Claims (1)

[Scope of Claims] 1. After impregnating wood with one of the components, a polymerization initiator and a polymerization accelerator, impregnating the other component with a vinyl monomer or oligomer and heating at 60°C.
A method for producing a wood-plastic composite material, which comprises polymerizing in the following steps. 2. After storing wood in a sealed container and degassing the wood by reducing the pressure in the container, a solution containing either a polymerization initiator or a polymerization accelerator is injected into the container from the first storage tank. After that, the excess solution is returned to the first storage tank and the pressure inside the container is reduced again, and then the liquid containing the other component and the vinyl monomer or oligomer is poured into the container from the second storage tank. A wood-plastic composite characterized in that the wood is injected and immersed at a temperature of 60°C or less, the excess liquid is returned to a second storage tank, and the wood is further left at the above temperature for a required period of time, and then the wood is taken out from the container. Method for manufacturing treated materials.