KR102128403B1 - Wood having hydrophobically modified surface - Google Patents

Abstract

The present invention relates to a wood surface-modified with hydrophobicity, and more specifically, by irradiating wood immersed in an alcoholic solvent in which 5 to 50 wt% of the hydrophobic monomer is mixed based on the total weight of the solvent, the hydrophobic monomer It relates to a hydrophobically modified wood surface, including a grafted hydrophobic wood surface.

Description

WOOD HAVING HYDROPHOBICALLY MODIFIED SURFACE}

The present invention relates to a wood surface-modified with hydrophobicity, and more particularly, to an environmentally friendly composite material in which the hydrophobic monomer is grafted on a wooden surface to improve the interfacial adhesion with the hydrophobic material and thus the mechanical properties of the material.

One of the problems of the plastics industry in recent years is the disposal of wastes generated after use, and petroleum-based plastics are difficult to biodegrade, and secondary pollution by landfilling and incineration occurs. In this regard, many researchers have shown much interest in the development of biodegradable plastic materials.

On the other hand, wood materials (wood) are environmentally friendly materials, and are widely used for construction and other materials. However, their use is limited due to their weak durability and disadvantages such as water absorption. In view of the development of a material supplemented with these drawbacks, research on biomass-based wood/biodegradable wood plastic composites has been actively conducted around Europe and North America. In particular, the development of new materials using waste wood powder is drawing attention from an economic, technical and environmental perspective.

However, there is a problem in that it is very difficult to obtain desired physical properties due to low interfacial adhesion between wood powder and polymer, and methods for improving their interfacial adhesion include adding basic compounds and compatibilizers. It is going on. For example, Japanese Patent No. 2549344 discloses a method of manufacturing a surface layer resin-infused wood, but does not directly modify the wood, but only a configuration of forming a resin layer on the surface, and replacing the hydrophobic resin in this technique. In this case, the problem of deteriorating the mechanical properties of the final product due to the deterioration of the interfacial adhesion with wood occurs.

Accordingly, when a technology capable of improving interfacial adhesion with a hydrophobic material is developed by modifying the wood itself with a hydrophobic monomer, even if the modified wood is mixed with a biodegradable polymer, an environmentally friendly composite material with improved mechanical properties is manufactured. It is expected to be widely applicable in related fields.

Accordingly, one aspect of the present invention is to provide a method for modifying wood to be hydrophobic.

Another aspect of the invention is to provide a hydrophobically modified wood.

Another aspect of the present invention is to provide a hydrophobic polymer composite material comprising a hydrophobically modified wood.

According to one aspect of the invention, the step of providing a solvent in which the hydrophobic monomer is mixed; Immersing wood in a solvent in which a hydrophobic monomer is mixed; And irradiating the solvent with which the wood is immersed, a method for hydrophobic modification of wood.

According to another aspect of the present invention, there is provided a hydrophobically modified wood by the method of the present invention.

According to another aspect of the present invention, a hydrophobic polymer composite material is provided, which includes a hydrophobically modified wood and a hydrophobic polymer.

According to the present invention, by manufacturing biomass-based biodegradable wood and plastic composite materials using radiation technology, it is possible to overcome the problems of physical properties and mass production due to low interfacial adhesion, which is a problem of the technology related to the production of composite materials.

1 is a graph showing the effect of radiation dose (a) and monomer concentration (b) on the irradiation grafting of TMPMA on wood flour.
2 is a photograph showing the results of water absorption experiments of unmodified wood powder, hydrophilic modified wood powder by MAAc, and hydrophobic modified wood powder by TMPMA.
3 is a graph showing the effect of radiation dose (a) and the type and concentration of monomer (b) on the water absorption rate in irradiation grafting of TMPMA on wood flour.
FIG. 4 is a photograph showing an example in which a PLA film containing no wood powder, a PLA film including unmodified wood powder, and a PLA film including modified wood powder are prepared.
5 is a comparison of the tensile strength of the PLA film containing the unmodified wood powder and the PLA film containing the unmodified wood powder and the PLA film containing the modified wood powder. It is a graph showing the effect of (a) and the type and concentration of the monomer (b).
6 schematically shows the surface adhesion of the unmodified wood powder upon cooling after heat-processing the film with the polymer resin and in the case of wood powder with a hydrophobic surface modification according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

Wood has the property of absorbing moisture, and when the surface is modified with a hydrophilic resin on wood, the absorption of moisture tends to increase, whereas the method of modifying wood with hydrophobicity is not commercialized. According to the present invention, there is provided a method of modifying hydrophobicity of wood, and according to the present invention, wood can be modified to hydrophobicity, thus reducing the water content of wood and significantly improving the interfacial bonding force when forming composite materials with hydrophobic materials. As a result, it is possible to provide a composite material having excellent physical properties.

More specifically, the hydrophobic modification method of wood according to the present invention comprises the steps of preparing a solvent in which a hydrophobic monomer is mixed; Immersing wood in a solvent in which a hydrophobic monomer is mixed; And irradiating the solvent with which the wood is immersed.

The solvent should be selected in consideration of the type of monomer and the subsequent treatment process, and the solvent that can be used in the present invention may be alcohol, and the alcohol may be methanol, ethanol, or a mixture thereof, for example, ethanol Can be used. When ethanol is used as a solvent, it is preferable because the solvent can be removed by vaporization of ethanol by heating at a subsequent treatment step.

The solvent in which the hydrophobic monomer is mixed preferably contains the hydrophobic monomer in an amount of 5 to 50 wt% based on the total weight of the solvent, and more preferably, in an amount of 5 to 30 wt%. When the content of the hydrophobic monomer is less than 5 wt% based on the total weight of the solvent, the modification of the hydrophobic monomer to the wood is not sufficient, so that the absorption rate of the hydrophobic modified wood is insufficient, and the increase in the interfacial bonding power with the hydrophobic material may not be large. In the case of exceeding 50 wt%, the improvement in the degree of hydrophobic modification is no longer significantly increased in preparation for the increase in the content of the hydrophobic monomer, and thus, it tends to be undesirable in the process economy.

The hydrophobic monomer that can be used in the wood modification of the present invention may be at least one selected from the group consisting of TMPMA (3-(Trimethoxysilyl)propyl methacrylate), DMEMA (2-(Dimethylamino)ethyl methacrylate) and DPEHA (dipentaerythritol hexaacrylate) And preferably TMPMA (3-(Trimethoxysilyl)propyl methacrylate), but is not particularly limited.

The wood to be modified in the present invention is not particularly limited, but may be, for example, wood powder. The wood is a fine powder of wood, and may be classified by passing 40 to 100 mesh, but the size of the powder is not particularly limited to the subject of modification of the present invention.

The radiation in the step of irradiating the radiation may be selected from the group consisting of gamma rays, electron beams, ultraviolet rays, and X rays, and is preferably gamma rays. In addition, the gamma ray can be emitted from any one of the radioactive isotopes selected from the group consisting of cobalt (Co)-60, krypton (Kr)-85, strontium (Sr)-90, and cesium (Cs)-137, preferably For example, the gamma ray may be cobalt (Co)-60, but is not limited thereto.

Meanwhile, the step of irradiating the radiation is performed at a dose of 25 to 200 kGy, for example, a dose of 25 to 100 kGy, preferably 25 to 75 kGy. When the dose of the radiation irradiation step is less than 25 kGy, the modification of the hydrophobic monomer for wood expression may be insufficiently performed, and when it is performed in excess of the dose of 200 kGy, the improvement of the modification due to the dose increase is insignificant. It is not desirable in terms of consumption and fair economy.

Furthermore, subsequent to the step of irradiating the radiation, washing with alcohol; And drying may be further performed.

The step of washing with alcohol may be the same as or different from the alcohol used as a solvent, and washing may be performed 2 to 5 times to remove unreacted monomers, oligomers, polymers, and the like.

The drying step subsequently performed in the washing step may be performed at a temperature of, for example, 35 to 90°C, and is preferably performed at a temperature of 40 to 85°C. If the drying temperature is less than 35°C, it takes a long time to dry, which is disadvantageous in the process economy. If it exceeds 90°C, there is a problem of fire due to ignition due to ethanol evaporation during high temperature drying.

The method of performing the drying step is not particularly limited, and may be performed, for example, by oven drying, hot air drying, high pressure drying, and the like, preferably, temperature control is possible from 30 to 90, and through hot air to the interior of the wood. It is performed by an oven drying method capable of uniform drying.

According to another aspect of the present invention, a hydrophobically modified wood is provided by the hydrophobic modification method of wood according to the present invention described above.

As mentioned in connection with the method for the hydrophobic modification of wood, in the present invention, the wood is not particularly limited and may be, for example, wood powder.

When the wood powder modified to hydrophobicity according to the present invention is significantly reduced in water absorption when mixed with water, it is possible to significantly improve the water resistance of the product when manufacturing various products using the material.

Further, according to another aspect of the present invention, a hydrophobic polymer composite material is provided, which includes a hydrophobically modified wood and a hydrophobic polymer.

The hydrophobically modified wood may be modified according to the hydrophobic modification method of the wood of the present invention as described above.

The hydrophobic polymer composite material may be, for example, a hydrophobic polymer film containing hydrophobically modified wood powder, but is not limited thereto, and includes all the products molded from a hydrophobic polymer film containing aqueous modified wood powder without limitation. Is to do.

For example, in the case of a hydrophobic polymer film containing hydrophobically modified wood powder, as shown schematically in FIG. 6, the wood powder that has not been modified upon cooling after heat processing the film has an interface adhesion with a polymer resin (PLA). Insufficient polymer resin shrinks and the interface is separated and the physical properties are deteriorated, but in the case of wood powder whose surface is modified with hydrophobicity according to the present invention, the interface adhesion with the polymer resin is improved, and thus the tensile strength, etc. The physical properties of can be remarkably improved.

On the other hand, the hydrophobically modified wood powder may be included in an amount of 1 to 50% by weight based on the total weight of the hydrophobic polymer composite material, preferably 6 to 35% by weight. When the wood-modified wood flour is less than 1% by weight based on the total weight of the hydrophobic polymer composite material, the content of the wood-modified wood flour in the composite material is insignificant, and thus there is a tendency to insufficiently express the properties of the wood flour modified. If exceeded, the content of the hydrophobic polymer that serves to bond the modified wood powder is relatively small, so the durability of the composite material may be reduced.

The hydrophobic polymer material included in the hydrophobic polymer composite material is not particularly limited as long as it is a hydrogen polymer material. For example, the hydrophobic polymer is polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), Polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), acrylonitrile butadiene styrene copolymer (ABS) and acrylonitrile-styrene (acrylonitrile-styrene, ASA) may be at least one selected from the group consisting of, preferably polylactic acid (PLA).

When a film obtained by combining the wood powder and the hydrophobic polymer material modified by the present invention as described above is prepared, the surface energy of the highly polar wood powder is changed to non-polar, thereby increasing the interface adhesion between the wood powder and the hydrophobic polymer, thereby significantly increasing the mechanical properties. An improved composite film can be obtained.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples for helping the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

1. hydrophobically Modified Wood production

(1) Materials

Waste wood powder (average particle size 50 μm) produced after wood processing was obtained from G Biotech Co., Ltd. and dried in a drying oven at 90° C. for 48 hours. In addition, the reagent used for surface modification was 3-(Trimethoxysilyl)propyl methacrylate, Ethyl alcohol from Sigma-Aldrich, and was used without purification. PLA (poly(lactic acid)), a biodegradable polymer, is used by NatureWorks LLC. The company's products were used.

(2) Preparation of 3-(trimethoxysilyl)propyl methacrylate modified wood powder using gamma rays

3-(Trimethoxysilyl)propyl methacrylate (hereinafter referred to as'TMPMA') was added to ethanol to adjust the concentration to 0.5 to 30.0 wt% to prepare a mixed solution at room temperature. After 500 g of wood flour was placed in a 2 liter glass beaker, 1 liter of the mixed solution was poured and immersed, wrapped with aluminum foil, and stored at room temperature for 12 hours.

Subsequently, the mixed solution in which wood powder was immersed was irradiated with a radiation dose of 25 to 75 kGy at a radiation dose rate of 10 kGy/h using gamma rays generated at ⁶⁰ Co.

The surface-modified wood powder obtained as a result was washed 3 to 4 times with ethanol to remove unreacted monomers, oligomers, homopolymers, etc., and then dried in a 75°C dryer for 1 day to obtain a final modified wood powder.

2. Modified Woody Graft rate Confirm

In order to measure the graft ratio of TMPMA-modified wood powder by radiation, it was calculated using the following equation (1). W _o is the dry weight of wood powder before radiation graft, W _f Is the weight of the grafted wood flour.

Graft rate (Degree of Grafting, %) = [( W _f -W _o ) _/ W _o ] × 100 ... Equation (1)

Figure 1 (a) is the grafting rate of TMPMA-modified wood flour when the radiation dose is increased to 25, 50, 75 kGy by immersing wood flour at a concentration of 30 wt% of 3-(Trimethoxysilyl)propyl methacrylate (TMPMA) dissolved in ethanol. Is a graph showing an increase from 7.32±0.46% to 38.10±1.57%.

When an ethanol solvent having a TMPMA concentration of 30 wt% was used, it was confirmed that the graft ratio of wood flour was low at 25 kGy with the radiation direction, but at 50 kGy or higher, the amount of TMPMA modified on the surface of the wood flour was significantly increased. In order to ionize the methacrylate of TMPMA, it was found that a radiation dose of 25 kGy or more was required.

On the other hand, when the radiation dose was fixed at 75 kGy and the concentration of 3-(Trimethoxysilyl)propyl methacrylate (TMPMA) was 0.5 to 1 wt%, the graft ratio was less than 2.34±0.66% to 2.55±0.42%, but TMPMA 5 to 5 From the 30 wt% concentration, it was confirmed that the increase was significantly from 22.30±4.02% to 38.10±1.57%. This indicates that as the concentration of monomer per unit area increases, the more methacrylate chains of 3-(Trimethoxysilyl)propyl methacrylate (TMPMA) at the same radiation dose, the greater the amount that can be grafted on the surface of wood powder.

According to the results of this experiment, the concentration of the monomer is 5 to 30 wt% and the radiation dose is 25 to 75 kGy as a condition for the ionization of the hydrophobic monomer TMPMA due to the radiation ionization energy when the wood powder is surface-treated. It was confirmed that it was a graft.

3. Modified Woody Water uptake

It was calculated using Equation (2) to measure the moisture content of 3-(Trimethoxysilyl)propyl methacrylate modified with radiation. W _o is the dry weight of wood powder before immersion in distilled water, W _f Is the weight of wood powder after immersion in distilled water for 1 day.

Water content (Degree of Grafting, %) = [( W _f -W _o ) _/ W _o ] × 100 (2)

In order to measure the moisture content of the modified 3-(Trimethoxysilyl)propyl methacrylate (TMPMA) hydrophobic monomer and the hydrophilic monomer Methacrylic acid (MAAc) by radiation, the weight of the powder was measured after dipping in distilled water for 1 day.

Fig. 2 shows the surface of the wood (left) that is not surface-treated with radiation, the wood (Medium) where hydrophilic monomer Methacrylic acid (MAAc) has been surface-treated by radiation, and the hydrophobic monomer, 3-(Trimethoxysilyl)propyl methacrylate (TMPMA). This is a photograph that visually checks the water content when the treated wood powder (right) is added to distilled water. The untreated wood powder and the hydrophilic monomer Methacrylic acid (MAAc) surface-treated wood powder subside in water in a few seconds when placed in distilled water, but the hydrophobic monomer 3-(Trimethoxysilyl)propyl methacrylate (TMPMA) is surface-treated. Wood flour could be seen floating on the surface of distilled water even after a day.

FIG. 3 graphically shows the water content according to the radiation dose (FIG. 3(a)) and according to the TMPMA concentration (FIG. 3(b) ).

Figure 3 (a) shows a change in water content according to the radiation dose for 30 wt% TMPMA grafted wood powder, as shown in Figure 3 (a), the moisture content of the wood grafted hydrophobic monomer by irradiation It was confirmed that this was remarkably lowered, and more specifically, it was confirmed that the water content could be lowered to less than 10% while the dose increased from 25 kGy to 75 kGy.

On the other hand, Figure 3 (b) shows a change in water content according to the concentration of TMPMA in the solvent when irradiated with 75 kGy radiation, as shown in Figure 3 (b), the water without hydrophobic surface treatment with radiation is close to 100% water It was confirmed that the moisture content of the poly(TMPMA) with hydrophobicity increased as the water content of wood powder grafted with 5 wt% TMPMA decreased to 78±3.10%. In addition, the moisture content of wood powder grafted with 15 wt% to 30 wt% TMPMA was reduced to 10.35±1.0145 to 1.47±0.78%, and the surface of wood flour (wood-based cellulose) containing hydrophilic group OH was used for radiation. It was confirmed that the water content of the grafted wood content of the hydrophobic (trimethoxysilyl)propyl methacrylate) monomer can be lowered.

As a result of this experiment, it was confirmed that the hydrophobicity of wood powder was increased by poly(TMPMA) surface-treated by radiation, and materials such as a biodegradable polymer having a hydrophobic group and a film in which wood powder modified by hydrophobicity was composited by the present invention were prepared. It can be seen that the surface energy of highly polarized wood powder is changed to non-polar, thereby increasing the interfacial adhesion between wood powder and synthetic polymers, thereby making it possible to manufacture composite films with improved mechanical properties.

4. Modified Wood powder Measurement of tensile strength of films produced using ( Instron )

In order to prepare a composite film of wood/polymer modified with 3-(Trimethoxysilyl)propyl methacrylate by radiation, the weight ratio of polylactic acid (PLA) polymer and hydrophobic modified wood powder was mixed at 80:20 (wt%). At this time, the hydrophobically modified wood powder was used as a powder irradiated with 75 kGy using a solvent having a TMPMA concentration of 30 wt %. After fixing the temperature of the mixer at 190°C to dissolve PLA, add wood powder and mix for 3 minutes to prepare pellets. Using the prepared pellets, a polymer film (PLA/T- g -wood powder film, Preparation Example 1) containing modified wood flour was molded using a thermocompressor.

For comparison, a PLA film that does not contain wood flour (Comparative Production Example 1) was prepared, and a polymer film containing wood flour (PLA/wood powder film) by the same process as described above, except that unmodified wood powder was used. , Comparative Preparation Example 2) was prepared.

The three films of Preparation Example 1, Comparative Preparation Example 1 and Comparative Preparation Example 2 prepared as described above are shown in FIG. 4, and instron was used to measure their tensile strength.

Figure 5 shows the results of measuring the tensile strength of the three films using a thermocompressor, the tensile strength of the PLA film of Comparative Production Example 1 was 20.16 ± 1.14 MPa.

On the other hand, in the PLA / wood powder film of Comparative Preparation Example 2, when the content of wood powder is PLA: wood powder = 80:20 weight ratio, the tensile strength of the film containing the unmodified wood powder is 12.92 ± 0.70 MPa, wood powder It was confirmed to be reduced by about 8 MPa by inclusion.

However, in the PLA/modified wood powder film of Preparation Example 1, when the content of the modified wood powder with the same content as above is PLA:modified wood powder = 80:20 weight ratio, the radiation dose as shown in Figure 5(a) It was confirmed that the tensile strength of the film was increased to 13.97±1.97 MPa, 16.08±1.95 MPa, and 17.78±0.24 MPa when the film was increased to 25 kGy, 50 kGy, and 75 kGy. The modified wood flour in this experiment was modified using a solvent containing 30 wt% TMPMA.

On the other hand, as shown in Figure 5 (b), when the radiation dose is fixed to 75 kGy, and when increasing the concentration of TMPMA in the solvent when preparing the modified wood powder, the more the modified wood powder using a solvent with an increased concentration of TMPMA It was found that the tensile strength of the film containing the modified wood flour increased.

In the manufacture of PLA and composite materials that are wood-grafted with a hydrophilic group -OH group containing OH group (woody cellulose) and grafted with a hydrophobic group TMPMA (trimethoxysilyl)propyl methacrylate) monomer, and biodegradable polymer and hydrophobic group, It was confirmed that the physical properties such as tensile strength increased than the PLA composite film in which wood powder without surface treatment was mixed.

As shown schematically in FIG. 6, the wood powder that has not been modified upon cooling after thermal processing of the film has insufficient interface adhesive strength with the polymer resin (PLA), resulting in the polymer resin shrinking and separating the interface, thereby deteriorating physical properties. In the case of wood powder whose surface is modified with hydrophobicity according to the present invention, the interfacial adhesion with the polymer resin is improved, so that physical properties such as tensile strength can be remarkably improved as the interface maintains a stable bond. Modified hydrophobic group TMPM It can be confirmed experimentally that the surface adhesion of (trimethoxysilyl)propyl methacrylate) and hydrophobic PLA is increased.

Therefore, when manufacturing a film in which wood powder and a hydrophobic polymer material modified by the present invention are composited, the surface energy of wood with high polarity is changed to non-polarity, thereby increasing the interface adhesion between wood and hydrophobic polymers to obtain a composite film with improved mechanical properties. You can do it.

Although the embodiments of the present invention have been described in detail above, the scope of rights of the present invention is not limited to this, and various modifications and variations are possible without departing from the technical spirit of the present invention as set forth in the claims. It will be obvious to those of ordinary skill in the field.

Claims (10)

Hydrophobic surface-modified, including a hydrophobic wood surface in which hydrophobic monomers are grafted by irradiating wood immersed in an alcoholic solvent in which 5 to 50 wt% of a hydrophobic monomer is mixed based on the total weight of the solvent. wood.
The hydrophobically modified wood of claim 1, wherein the alcohol is methanol, ethanol or a mixture thereof.
The hydrophobic surface of claim 1, wherein the hydrophobic monomer is at least one selected from the group consisting of TMPMA (3-(Trimethoxysilyl)propyl methacrylate), DMEMA (2-(Dimethylamino)ethyl methacrylate) and DPEHA (dipentaerythritol hexaacrylate). This modified wood.
The wood of claim 1, wherein the wood is wood flour.
The method of claim 1, wherein the radiation of the step of irradiating the radiation is selected from the group consisting of gamma rays, electron beams, ultraviolet rays and X-rays, hydrophobically modified wood.
The hydrophobically modified wood of claim 1, wherein the irradiated radiation is a dose of 25 to 200 kGy.
A hydrophobic polymer composite comprising the hydrophobically modified wood and hydrophobic polymer of any one of claims 1 to 6.
The hydrophobic polymer composite material according to claim 7, wherein the hydrophobic polymer composite material is a hydrophobic polymer film containing wood having a hydrophobic surface.
The hydrophobic polymer composite material according to claim 7, wherein the hydrophobically modified wood is contained in an amount of 1 to 50% by weight based on the weight of the total hydrophobic polymer composite material.
According to claim 7, The hydrophobic polymer is polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl cro Ride (PVC), At least one selected from the group consisting of acrylonitrile butadiene styrene copolymer (ABS) and acrylonitrile-styrene (ASA), a hydrophobic polymer composite material.

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