JPS62184803A - Manufacture of wood-plastic composite body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for manufacturing a wood-plastic composite with excellent dimensional stability.

[Conventional technology]

In general, wood has the property of swelling and contracting when it absorbs and releases moisture, which causes warping and cracking, which ultimately leads to a decrease in strength. The reason for this is that when moisture moves in wood, the moisture near the surface of the wood evaporates first and causes drying shrinkage, but inside the wood the moisture content is high and does not shrink. It is thought that stress is generated at the boundary between drying shrinkage and unresolved elasticity, and warping and cracking occur when this stress is released. In particular, near the end of the wood, the movement of water in the direction of the fibers is significantly faster than the movement of water in the radial and tangential directions, so the end surface dries and shrinks quickly, creating tensile stress, which is thought to cause frequent wood cracks. It is considered.

Traditionally, formal methods, acetylation methods,
Heating methods, cyanoethylation methods, alkyl ketene dimer treatments, ethylene oxide treatments, etc. are known, but these methods have drawbacks such as weakening of the wood, difficulty in implementation, and large cost increases, and none of them are practical. It has not yet become a reality.

On the other hand, in recent years, a swelling zone filling method and a monomer impregnation method have been proposed as wood treatment methods different from the above methods. Among these, the swelling zone filling method is a method in which the voids of wood are impregnated with an appropriate polymer, and the monomer impregnation method is a method in which a polymerizable monomer is impregnated into the voids of wood and then polymerized. be. The wood treated by these methods becomes a so-called wood-plastic composite consisting of wood and a polymer held in the voids, and the hardness and tensile strength of the wood vary depending on the type of polymer. It has the characteristic that physical properties such as strength 1 bending strength can be greatly improved.

[Problem that the invention seeks to solve]

However, in terms of improving the dimensional stability, which is the drawback of wood, the above two treatment methods cannot necessarily be said to be effective methods for the following reasons.

First, in the swelling region filling method described above, polyvinyl alcohol and polyethylene glycol are known to be applicable polymers, but among these, low molecular weight polyethylene glycol has relatively good dimensional stability. can get. However, because this polymer has a low molecular weight, it is liquid or semi-solid at room temperature, and therefore a wetting phenomenon appears on the surface of the treated wood or composite when administered orally.
Subsequent painting becomes difficult.

In addition, various monomers such as methyl methacrylate, styrene, 2-hydroxyethyl acrylate, and polyoxyalkylene glycol (meth)acrylate are known to be applicable to the monomer impregnation method. Even if you use selectively,
The dimensional stability of wood cannot be sufficiently improved unless the polymer retention rate after impregnation polymerization is set to a high retention rate of 40 to 90ffii%, and such a high polymer retention rate makes the production cost of the composite extremely high. Become.

Therefore, in obtaining a wood-plastic composite that is effective in improving the physical properties of wood as typified by the above two treatment methods, the present invention is capable of producing a wood-plastic composite that is effective in improving the physical properties of wood, without causing the above-mentioned conventional problems. The above composite with highly improved dimensional stability can be produced without causing problems such as wetting phenomena on the body surface that makes subsequent painting difficult, or increased production costs due to polymer retention. The purpose is to obtain.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors found that among the above two treatment methods, a method belonging to the swelling zone filling method, which is a method that is conventionally used as a polymer for wood filling applied to this method, was found. The realization that a wood-plastic composite with highly improved dimensional stability could be produced without the aforementioned problems by using a specific polymer that had never been used before, led to the completion of this invention. It's arrived.

That is, this invention provides wood with the following formula; % formula % (wherein R1 is hydrogen or a methyl group, R2 is
30 alkyl group or alkenyl group) alone or a copolymer of a (meth)acrylic acid ester monomer represented by the above, or a copolymer of the above monomer and another monomer copolymerizable with the above monomer. The present invention relates to a method for producing a wood-plastic composite (hereinafter abbreviated as WPC).

As described above, in this invention, a specific polymer or copolymer containing the (meth)acrylic acid ester monomer represented by the above formula as an essential monomer component is used as the polymer to be impregnated and filled into wood. This polymer contains in its molecule an alkyl group or alkenyl group having 4 to 3 carbon atoms derived from the above-mentioned monomer, that is, a highly lipophilic group having a large number of carbon atoms. Compared to polymers used in the swelling zone filling method as well as polymers made by combining monomers such as methyl methacrylate that were used in the monomer impregnation method, this polymer has extremely high lipophilicity. have.

Therefore, when this polymer is impregnated into wood, high water repellency is imparted to the wood, and the hygroscopicity of the wood is significantly reduced. As a result, the moisture absorption and desorption properties that cause warping and cracking of the wood are reduced, and the generation of internal stress is suppressed, so that the resulting WPC exhibits extremely excellent dimensional stability. Due to the characteristics of the polymer mentioned above, this dimensional stability can be obtained even if the retention rate of this polymer in the wood is very small compared to the conventional swelling zone filling method or monomer impregnation method. Therefore, a favorable result is brought about in reducing the production cost of WPC. Moreover, this polymer essentially does not pose any particular risk of causing problems such as the phenomenon of wetting appearing on the surface of the composite during oral administration, which makes subsequent coating difficult, as seen in the conventional swelling region filling method.

[Structure and operation of the invention]

Wood used in this invention includes softwood, hardwood,
Or there is no need to distinguish between domestic and foreign materials. Further, it can be applied to all forms of wood such as logs, logs, square columns, cylinders, and sawn boards.

In the (meth)acrylic acid ester monomer represented by the above formula in this invention, the alkyl group or alkenyl group must have 4 to 30 carbon atoms. The reason for this is that when the number of carbon atoms is less than 4, the lipophilicity of the polymer decreases, and when the number of carbon atoms exceeds 30, it is difficult to obtain, and there are problems such as poor impregnation into wood.

Specific examples of such (meth)acrylic acid ester monomers include n-butyl (meth)acrylate, 1s
o-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate,
Lauryl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, heptyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, oftacocil (
meth)acrylate, oleyl(meth)acrylate,
Examples include palmitrail (meth)acrylate. Moreover, there is no problem even if it is a mixture of these.

In this invention, a homopolymer or copolymer of the above (meth)acrylic acid ester monomer may be used, or a copolymer of the above monomer and another monomer copolymerizable with it may be used. It's okay.

In addition, when using a copolymer of the (meth)acrylic acid ester monomer represented by the above formula and another monomer that can be copolymerized with this, the above (meth)acrylic acid ester monomer accounts for all the monomers. In general, it is desirable that the content is 5% by weight or more, preferably 10% by weight or more. If this ratio is too small, sufficient dimensional stability cannot be obtained.

On the other hand, as the amount used increases, the dimensional stability improves (although it is generally preferable that the amount is 20% by weight or more).

Other copolymerizable monomers include those represented by the same formula as above except that the alkyl or alkenyl group has less than 4 carbon atoms, such as methyl (meth)acrylate and ethyl (meth)acrylate. (Meth)acrylic acid ester monomers, styrene, (meth)acrylonitrile, vinyl acetate, etc. that are often used as modifying monomers in general (meth)acrylic polymers, 2-hydroxy (meth)acrylate, polyethylene glycol monomers, etc. Examples include hydroxyl group-containing monomers such as (meth)acrylate, acid group-containing monomers such as (meth)acrylic acid and maleic anhydride, and epoxy group-containing monomers such as glycidyl (meth)acrylate.

In this invention, when impregnating wood with a specific polymer as described above, a polymer solution is prepared by dissolving the above polymer in an appropriate organic solvent in advance. There is 411. used here. As a solvent, methanol, ethanol,
Examples include polar solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, and dioxane, as well as nonpolar solvents such as toluene and xylene. The degree of polymer per volume t (l) of this polymer is 0.5 to 50% by weight, preferably 1 to 30% by weight.
It is.

It is also possible to add other additives, such as rust preventives, preservatives, and other substances that do not impede the object of the present invention, to the above polymer solution, if necessary.

To impregnate wood with such a polymer solution, the wood is first subjected to a drying process such as air drying, heat drying, or heat drying under reduced pressure to reduce the water content in the wood to 8 to 1.
Adjust the humidity to a range of about 8% by weight. Next, this wood is sealed in a vacuum container, and after reducing the pressure inside the container with a vacuum pump or the like to remove gas in the wood, a polymer solution is poured into the container, and the inside of the container is returned to atmospheric pressure. As a result, the solution is impregnated into the voids of the wood. Pressure impregnation may also be used to facilitate the impregnation.

After being impregnated in this manner, the solvent is removed from the wood by drying such as natural drying, heat drying, or reduced pressure drying, thereby obtaining WPC in which the specific polymer is impregnated and retained in the wood. I can do it. The polymer retention rate of this WPC is generally 1 to 35% by weight, especially 5 to 3% by weight.
The amount can be set to a much smaller amount than the conventional treatment method, which is approximately 0% by weight, and this provides good dimensional stability that can be applied to a variety of applications. of course,
Depending on the purpose of use of WPC, in order to improve its physical properties and to achieve a higher degree of dimensional stability, the polymer retention rate may be higher than the above, for example, up to about 50% by weight.
Furthermore, it is also possible to set the retention rate as high as about 110% by weight.

In addition, in this specification, polymer retention rate refers to WP
It means the weight ratio of the polymer to the wood constituting C, that is, the value calculated by the following formula.

X: Absolute dry weight of WPC Y: Absolute dry weight of untreated wood [Effects of the invention] As described above, according to the method of this invention, the phenomenon of wetting appears on the surface of the composite orally and the subsequent coating It is possible to manufacture WPC that exhibits excellent dimensional stability and greatly suppresses the moisture absorption swelling and moisture release shrinkage characteristic of wood, without causing problems such as difficulty in polymer retention or increased production costs due to polymer retention. It can be manufactured advantageously. For this reason, WPC obtained by this method is particularly suitable for use in external walls and flooring materials that are constantly exposed to humidity and dryness, wooden works of art, and other building materials that require a high degree of dimensional stability. It can also be used for various purposes.

〔Example〕

Next, examples of the present invention will be described in more detail. Note that the polymer solutions A-F for impregnating wood used in the following examples and the polymer solutions G-J for impregnating wood used in comparative examples were each prepared by the following methods. In the text, parts mean parts by weight.

Polymer Solution A> 210 parts of xylene was charged into a four-hole flask equipped with a stirrer, a thermometer, and a condenser, and the interior was purged with nitrogen, and the temperature was raised while stirring to reflux the xylene. After the reflux started, a mixed solution of 50 parts of stearyl methacrylate, 450 parts of methyl methacrylate, and 12 parts of tert-butylperoxyoctoate was added dropwise over 2.5 hours. During this time, the reflux temperature was controlled to be maintained. After the dropwise addition was completed, the mixture was aged under reflux for 1 hour, and then a mixed solution of 12 parts of tert-butylperoxyoctoate and 40 parts of toluene was added, and the mixture was further aged under reflux for 1 hour. Thereafter, it was cooled and 250 parts of toluene was added to obtain a uniform polymer solution A.

Polymer? Volume B> Polymer solution B was prepared in the same manner as polymer solution A, except that the amount of stearyl methacrylate used was changed to 75 parts, and the amount of methyl methacrylate used was changed to 425 parts.

Polymer solution C> Same as polymer solution A except that the amount of stearyl methacrylate used was changed to 150 parts, the amount of methyl methacrylate used was changed to 300 parts, and 50 parts of styrene was used as another monomer. A polymer solution C was prepared.

Polymer? Volume D> A polymer solution was prepared in the same manner as in Polymer Solution A, except that the amount of stearyl methacrylate used was changed to 250 parts, and the amount of methyl methacrylate used was changed to 250 parts.

Polymer solution E> Except that 250 parts of 2-ethylhexyl methacrylate was used instead of 250 parts of stearyl methacrylate.
Polymer in the same way as in the case of polymer solution? Eight rounds of liquid E were prepared.

Polymer solution F> Polymer solution F was prepared in the same manner as polymer solution A, except that 500 parts of 1so-methyl methacrylate was used instead of 50 parts of stearyl methacrylate and 450 parts of methyl methacrylate. .

Polymer Solution G> Instead of 50 parts of stearyl methacrylate and 450 parts of methyl methacrylate, 500 parts of methyl methacrylate
Polymer solution G was prepared in the same manner as in the case of polymer solution A, except that the polymer solution G was used.

<Polymer 7 volume solution H> Polymer solution H was prepared in the same manner as polymer solution A except that 500 parts of styrene was used instead of 50 parts of stearyl methacrylate and 450 parts of methyl methacrylate.

Example 1 Tangential direction: 10 mm, radial direction: 70 mm, fiber direction: 130 mm
Straight-grained American cypress wood with a water content of 13% by weight and measured to mm was placed in a desiccator and the pressure was reduced to 10 mmHg. An impregnating solution prepared by diluting polymer solution A with acetone to a polymer concentration of 15% by weight was put into this desiccator, and after being impregnated under reduced pressure for 5 minutes,
The pressure was returned to normal, and the mixture was allowed to stand for 10 minutes, and then taken out from the desiccator.

This impregnated wood was air-dried for 72 hours and then dried at 80° C. for 16 hours to obtain wpc as an absolutely dry sample.

The polymer retention rate of this WPC was 21.0% by weight. In addition, in calculating the polymer retention rate, the untreated wood was dried in exactly the same manner as above to obtain its absolute dry weight, and the calculation was performed using the above-mentioned method from this and the absolute dry weight of the wpc.

Examples 2 to 6 Five types of WPC were obtained in exactly the same manner as in Example 1, except that polymer solutions B to F were used instead of polymer solution A. The polymer retention rates of these WPCs were as shown in Table 1 below.

Table 1 Comparative example 1. 2 Polymer solution G instead of polymer solution A.

Two types of W were prepared in the same manner as in Example 1 except that H was used.
I got a PC. The polymer retention rates of these WPcs were as shown in Table 2 below.

For each wpc according to the examples and comparative examples shown in Table 2 and above, the water absorption rate and volumetric swelling rate were measured, and from these measured values, each wpc was
Anti-water absorption capacity (RWA) and anti-swelling capacity (A S E
) The results of the investigation were as shown in Table 3 below.

The water absorption rate and volumetric swelling rate were measured using the following method.

Water absorption rate〉 WPC as an absolutely dry sample was completely immersed in water at 20°C and left for a specified number of days, and from the weight after standing (Xt) and the absolute dry weight before standing (X), the following was calculated. Calculated using the formula.

Xt-X water absorption rate (weight %) = -X 10. O〈Volume swelling rate〉 WPC as an absolutely dry sample is completely immersed in water at 20°C and left for a predetermined number of days, and from the volume after standing (Mt) and the volume before standing (M), the following is calculated. Calculated using the formula.

In addition, anti-water absorption capacity (RWA) and anti-swelling capacity (ASE) are determined by measuring the water absorption rate and volumetric swelling rate of untreated wood in the same manner as in the case of WPC above, and comparing this with the water absorption rate and volumetric swelling rate of WPC. From this, it was calculated using the following formula 2.

e c Wc: Water absorption rate of untreated wood Wt: Water absorption rate of WPC ■C: Volumetric swelling rate of untreated wood Vt: Volumetric swelling rate of WPC Note that the number of days left for measurement of water absorption rate and volumetric swelling rate was 4, respectively. 1 day and 7 days, but the water absorption rate and volume swelling rate calculated under the above measurement conditions are generally about 1
Equilibrium is reached after a week.

Table 3 As is clear from the results in Table 3 above, Examples 1 to 6
The WPC according to Comparative Example 1.2 shows excellent dimensional stability even though the polymer retention rate is in the range of 20 to 30% by weight, whereas the WPC according to Comparative Example 1.2 has a polymer retention rate of 20 to 30% by weight. It can be seen that low impregnation rates in the range of ~30% by weight do not exhibit good dimensional stability.

Note that the WPCs according to Examples 1 to 6 above do not show any wetting phenomenon on the surface of the WPCs over time even if they are left at room temperature for a long period of time. Even when the surface was painted normally, no problems such as difficulty in painting occurred.

Claims (1)

[Claims] (1) The wood contains the following formula; ▲ There are mathematical formulas, chemical formulas, tables, etc. 1. A method for producing a wood-plastic composite, which comprises impregnating a (meth)acrylic acid ester monomer alone or a copolymer thereof, or a copolymer of the above monomer and another monomer copolymerizable with the above monomer.