JPH0788434B2 - Method for producing wood-based foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to an effective and simple method for producing a wood-based foam excellent in physical properties such as density, compressive stress and elastic modulus,
More specifically, it relates to a method for producing a wood-based foam, which comprises foaming and hardening a wood solution prepared from untreated wood.

2. Description of the Related Art Conventional technology and its problems One of the conventional methods for utilizing wood materials is a technology for kneading wood powder and a foaming resin to obtain a foam (synthetic wood), which is widely known. However, in the case of this foam, wood flour only serves as a filler or aggregate,
It cannot be said that the characteristics of wood materials are effectively used. Despite the desire for effective use of wood-based resources, until now, wood-based materials themselves have not been able to obtain foams of wood-based materials that take advantage of their characteristics due to their active involvement in resinification. The reason is that it is not practical because it is difficult to dissolve wood in various solvents as it is, and even if it dissolves, it is difficult to prepare a wood solution suitable for a polymer reaction for producing a foam.

On the other hand, as a part of effective use of wood materials, it has been proposed to utilize properties of polyols such as lignocellulose, which is a component of wood materials, as a resin raw material for adhesives and films. For example, after a chemical modification such as esterification or etherification is performed on a part or all of the hydroxyl groups of a wood material (hereinafter, generally referred to as lignocelluloses such as wood) in an organic solvent. A wood solution was prepared by dissolving the wood solution, and a method of resinifying the wood solution was proposed (JP-A-57-2360, 60-104513, 60-206883,
61-215675-9, etc.). However, in these conventional examples, there is almost no specific description regarding the formation of the foam, and an example of a practical foam production method suitable for industrialization cannot be found.

The present inventors have conducted extensive studies for the purpose of developing an effective method for obtaining a wood-based foam, but using an organic solvent capable of polymerizing, chemically modified wood in the presence of an acid catalyst. We succeeded in preparing a wood-based foam from a wood solution obtained by treating the wood (Japanese Patent Laid-Open No. 61-171744).
Issue). The method of the present invention was a previously unknown meaningful method, but since the step of chemically modifying the wood material in advance is required, the manufacturing process as a whole becomes complicated and It included the problem that the cost was high, and there was room for improvement. Therefore, the inventors of the present invention have conducted continuous research to develop a method for easily and inexpensively producing a wood-based foam that is physically comparable to many foams already on the market. Came.

A method for simply obtaining a wood solution has recently been disclosed in connection with the production of the above foam (Japanese Patent Laid-Open No. 61-261358). The method of this application consists of directly dissolving the wood material in phenols or bisphenols, but it is considered that the hydroxyl groups of the wood material in the obtained wood solution exist without being activated. That is, when such a wood solution is foam-cured, only the solvent, which is a reactive compound, reacts, the wood component does not actively participate in the reaction, and cannot contribute to the improvement of the physical properties of the foam. Presumed to be.

From the above circumstances, if an effective method suitable for industrialization for producing a wood-based foam having excellent physical properties from a wood-based material is developed, it will greatly contribute to the effective use of wood-based resources. Conceivable.

An object of the present invention is to provide a practical and effective method for producing a wood-based foam having excellent physical properties, which is suitable for industrialization.

Means for Solving the Problems The present inventors have prepared a wood solution prepared by dissolving a wood material in an organic solvent having an active group capable of polymerizing in the presence of an anhydride of a dibasic acid. It was found that a wood-based foam having extremely excellent physical properties can be obtained by adding a curing agent and, if necessary, a foaming agent to foam-curing, and completed the present invention.

The wood solution used for producing the wood-based foam of the present invention is
Lignocellulosics in general, that is, wood powder, wood fibers, wood chips, crushed veneer chips, etc., and wood materials containing plant fibers such as straw and chaff, by a novel method developed by the present inventors. Is prepared.

As the dibasic acid anhydride used for producing the wood solution, dicarboxylic acid anhydrides are preferable, and maleic anhydride and phthalic anhydride are particularly preferable. The amount of these acid anhydrides can be changed at any time depending on the type of compound, the purpose of use of the wood solution, etc., but usually 1 to 50 parts per 100 parts of wood material,
It is preferably 5 to 20 parts.

Examples of the solvent having an active group capable of polymerizing include polyhydric alcohols, phenols, vinyl monomers, and glycidyl compounds. Of these, polyhydric alcohols and polyhydric phenols are particularly preferable.
Polyhydric alcohols that can be used in the present invention include dihydric alcohols such as ethylene glycol, trihydric alcohols such as glycerin, and polymers such as polyethylene glycol (eg, polyethylene glycol 600). Examples of polyhydric phenols include phenol, resorcin, cresol, naphthol, catechol, bisphenol A, bisphenol F and the like. These are used alone, but can also be used as a mixture of two or more kinds, or as a mixture with another suitable solvent suitable for the purpose of the present invention.

Further, water or an appropriate solvent having a low boiling point such as lower alcohol or acetone may be added and coexisted from the beginning or during the dissolution to adjust the viscosity suitable for use.

The ratio of each component in the mixture of the solubilization reaction should be appropriately selected depending on the reagents used, reaction conditions, etc., but usually, by weight ratio, 1 to 50 parts of acid anhydride to 10 to 1000 of solvent.
It is preferable that it is contained in 100 parts by weight and 100 parts by weight of this is mixed. For example, 100 parts of wood material is added to a solvent prepared by adding 1 to 50 parts of maleic anhydride to 10 to 1000 parts of polyethylene glycol 600 (PEG600). More preferably, 5 to 20 parts of maleic anhydride and polyethylene glycol 600 (PEG60
0) Mix 10 to 100 parts and 100 parts of wood material. In this case, if desired, acetone (about 1 to 25%) may be added.

The wood solution used in the method of the present invention is obtained by heating the reaction mixture selected within the range of the above conditions to 200 to 300 ° C. Preferably, the reaction is carried out at about 220 to 250 ° C. with or without stirring. Generally, the reaction mixture is placed in a pressure resistant reaction tube made of stainless steel, sealed and the temperature is adjusted to about
The desired wood solution can be obtained by reacting at 250 ° C. for 30 minutes to 4 hours. The wood material content of the wood solution thus obtained is 10% by weight depending on the amount of raw material charged.
It is in the range of 90%.

The wood solution is foamed and hardened by adding a crosslinking agent or a hardening agent, and if necessary, a foaming agent.

The crosslinking agent or curing agent is appropriately selected depending on the type of solution, but a polyvalent isocyanate compound, a polyvalent glycidyl compound, a melamine derivative, or the like, which is usually used for producing a foam, can be used. Although the following examples show examples using polyvalent isocyanate (Millionate MR200), it is extremely easy for those skilled in the art to select a crosslinking agent or a curing agent suitable for the purpose of the present invention. It is not limited to the use of a particular cross-linking agent or curing agent. A catalyst may be added to accelerate the reaction, if necessary. It is obvious to a person skilled in the art what kind of catalyst is suitable depending on the kind of the crosslinking agent or the curing agent,
It can be appropriately selected from them. Examples of the catalyst include amines and acid anhydrides.

Examples of the foaming agent include ammonium carbonate, sodium bicarbonate, azodicarbonamide and the like, which are gasified by thermal decomposition, and low boiling point solvents such as Freon. Some isocyanates generate gas in the presence of water, and in that case, water may be added.

Foam curing can be performed according to the conventional conditions for obtaining a urethane resin or an epoxy resin. The reaction conditions can be variously changed depending on the solvent of the wood solution and the reagent used. The wood solution according to the present invention, by the presence of an acid anhydride such as maleic anhydride at the time of dissolution, polyaddition to the wood material component of maleic anhydride and further condensation occurs, at least, lignin in the wood material. The unsaturated groups between the side-chain α-carbon and β-carbon of the lignin are eliminated (reactivity of the phenolic hydroxyl groups and aromatic nuclei of the lignin is increased, and further the introduction of the reactive unsaturated group to the lignin is the result). Furthermore, it is predicted that a carboxyl group having higher reactivity than a hydroxyl group is introduced into the wood material and activated, and it is considered to be extremely useful as a raw material for producing a resin. This means that the former sample had a stronger carbonyl group absorption in the IR absorption spectrum of the wood solution prepared by treating untreated wood in the presence and absence of maleic anhydride without volatile components. Supported by (Fig. 1).

Since the wood solution according to the present invention has been activated as described above, a crosslinking agent such as polyisocyanate or a curing agent and, if necessary, an appropriate foaming agent are added to the solution, and the conditions for ordinary resinification reaction are added. When subjected to the foam hardening treatment below, the wood solution actively participates in the reaction. As a result, the wood component plays an important role in maintaining the shape during foaming, and gives a foam having excellent physical properties.

The wood solution of the present invention is useful for resinification by foaming and curing as it is, but when polyadded with ε-caprolactone or propylene oxide, it reacts more effectively and gives a resin having excellent physical properties. This is, as shown in the figure below,
Addition of an alcoholic hydroxyl group to the phenolic hydroxyl group of lignin, and addition of propylene oxide or ε-caprolactone to the alcoholic hydroxyl group of cellulose, lignin or hemicellulose in a position susceptible to steric hindrance to form a glucopyranose ring. It is considered to be caused by the action of pulling out from the aromatic ring and the like.

As described above, the fact that maleic anhydride is polyadded and further condensed to the wood component, and that propylene oxide and ε-caprolactone are polyadded to the thus obtained wood solution, Of wood solutions prepared in the presence and absence, and samples of them reacted with ε-caprolactone or propylene oxide
It was revealed by GPC analysis (measurement by gel permeation chromatography, differential refractometer and UV detector) (Fig. 2, A, B, C, D and Fig. 3, A, B, C, D). FIG. 2 is a GPC chart (differential refractometer) of a wood solution and a product obtained by polyadding propylene oxide or ε-caprolactone thereto (A: a solution prepared by adding maleic anhydride, B: maleic anhydride). What was made into a solution without adding,
C: solubilized wood: propylene oxide = 1: 5, D: solubilized wood: ε-caprolactone = 1: 5), and FIG. 3 is a similar GPC chart (UV detector). As is clear from these figures, the effect of condensation of maleic anhydride on the wood component and the polycondensation of polycondensation of propylene oxide or ε-caprolactone to the condensate is observed.
Such activation is preferable for the foam curing reaction from the viewpoint that isocyanate has higher reactivity with alcoholic hydroxyl groups than with phenolic hydroxyl groups.

Using triethylenediamine as a catalyst, the foamed molded product obtained by the method of the present invention from a wood solution obtained by polyadding ε-caprolactone includes a commercially available foamed product with a density as low as 0.03 (g / cm ³ ). It was shown to be comparable to. The content of the wood solution is closely related to the physical properties such as density, compressive strength and elastic modulus. Generally, the physical properties were the lowest when the wood content was 20 to 30%. This also indicates that the presence of wood solution is deeply involved in foam formation. On the other hand, a foam obtained by the method of the present invention from a wood solution in which ε-caprolactone is polyadded using Freon is a hard foam having fine homogeneous closed cells, and is compressed even when a load of 1 kgf is applied. It was found that the wood solution played an important role in maintaining its shape, exhibiting excellent characteristics that no deformation occurred. These facts are also apparent from Table 3 below, which compares the characteristics of the wood-based urethane foam of the present invention and the commercially available urethane foam.

Further, in the method of the present invention, a wood-based foam having different physical properties can be obtained by changing the content of the wood component in the wood solution. That is, as a result of examining the mixing ratio of the wood material and PEG in the wood solution, the higher the wood material ratio, the lower the density of the foam, and the 25% compressive deformation stress and compression elastic modulus. descend. This is
It means that the higher the content of wood in the form of wood solution, the higher the porosity and the more prominent the soft foam-like properties. This is also related to the fact that the wood-based material is actively involved in the formation of the foam, and the wood-based foam obtained by the method of the present invention is structurally stable and has a very high porosity. It shows that the foam is large, flexible, and has excellent physical properties and is comparable to commercially available products.

Effect In the method of the present invention, a wood solution obtained from an untreated wood material is used to foam and harden it using a wood solution suitable for resinification, so that a wood foam excellent in physical properties such as density, compressive stress and elastic modulus can be obtained. It can be easily obtained. Therefore, it can be said that such a foam production method of the present invention and the obtained wood-based foam are valuable for effective use of wood.

Hereinafter, the present invention will be described in more detail with reference to production examples and examples.

Production Example 1 Preparation of Wood Solution 20 g of dried citrus wood flour (20 to 80 mesh), 15 g of polyethylene glycol 600 (PEG600), 4 g of maleic anhydride, and 10 ml of acetone were placed in a stainless reaction tube and sealed, and then at 250 ° C. After standing for 2.5 hours, a wood solution was obtained.

After removing volatile components from the obtained wood solution, IR spectrum was measured. For comparison, solubilization was carried out in the absence of maleic anhydride, and the resulting wood solution was treated in the same manner to measure IR. The results are shown in FIG. As is clear from the figure, the wood solution (A) obtained in the presence of maleic anhydride showed stronger absorption of carbonyl groups than the one in the absence (B). Have been introduced into the constituents of the wood material.

Production Example 2 Preparation of Wood Solution Using phthalic anhydride instead of maleic anhydride, the solution reaction was carried out in the same manner as in Production Example 1 to obtain a wood solution.

Example 1 Production of a wood-based foam from a hydroxypropylated wood solution 1. Hydroxypropylation of a wood solution The wood solution obtained in Production Example 1 in the amounts shown in Table 1 below,
Propylene oxide and potassium hydroxide were weighed out in a reaction vessel of a simple chemical reaction apparatus TEM-MV50 type, sealed, and reacted at 110 ° C for 2 to 4 hours under stirring (hydroxypropylation). The pressure first increased to 7 to 8 kgf / cm ^{2 with} increasing temperature, but then dropped and after 2 to 4 hours, 0 to 0.5 kgf / c 2.
It became m ² . Next, the solution-like product was neutralized with acetic acid, unreacted propylene oxide and water were removed under reduced pressure using a rotary evaporator, and the mixture was cooled to room temperature.

2. Production of Foam Hydroxypropylated Wood Solution 10 Prepared in Example 1.1
g, polyvalent isocyanate compound (Millionate MR200) 10
g, 0.25 ml of 10% aqueous solution of triethylenediamine (catalyst) (water acts as a foaming agent), and 0.20 g of Stahome F (foaming preparation agent) were mixed and vigorously stirred to foam. Further, it was cured at 90 ° C. for 2 hours.

The foam molded product thus obtained has a density of 0.03 to 0.
It was 04 g / cm ³ , and had excellent properties as a semi-rigid foam. The amount of propylene oxide added, that is, the dilution rate of the wood material in the wood solution (wood solution (g) / (wood solution (g) + propylene oxide (g)) and the physical properties of the foam (density, compressive stress, elastic modulus, And yield stress) are shown in FIGS. 4, 5, 6, and 7, respectively.

For comparison, only polyethylene glycol (PEG) 600 (10 g) was used in place of the wood solution, and 5 g of polyisocyanate compound (Millionate MR200), 0.20 ml of 10% triethylenediamine aqueous solution, and 0.20 ml of Stahome F were used to foam. When prepared, volume contraction occurs immediately after foaming,
A soft foam having a density of 0.18 g / cm ³ and a very small expansion ratio was obtained. This indicates that the wood solution plays an important role in molding the foam, especially in maintaining the shape during foaming.

Example 2 Production of a foam from a wood solution for ε-caprolactone polyaddition 1. Ring-opening polymerization of ε-caprolactone into a wood solution The wood solution obtained in Preparation Example 2 in the amounts given in Table 2 below,
Epsilon-caprolactone and potassium hydroxide were weighed and sealed in a reaction vessel of a simple chemical reaction apparatus TEM-MV50 type, and sealed, and reacted at 180 ° C for 1 hour under stirring. The internal pressure is 2 kg with the reaction
Increased to f / cm ² . Next, the solution-like product is neutralized with acetic acid, and reduced to 150 ° C. under reduced pressure using a rotary evaporator.
Then, unreacted ε-caprolactone and water were removed, and the mixture was cooled to room temperature.

2. Production of Foam 2.1 Method Using Water in Aqueous Triethylenediamine Aqueous Solution as Foaming Agent 10 g of the wood solution polyadded with ε-caprolactone prepared in the above Example 2.1 was kept at 50 ° C. to give a polyvalent isocyanate compound (Millionate MR200) 10 g, triethylenediamine (catalyst) 10% aqueous solution 0.20 ml, and home F
(Foaming preparation) 0.20 g was mixed and vigorously stirred to foam. Further, it was cured at 90 ° C. for 2 hours.

The foam molded article thus obtained has a density of 0.03 g / cm 3.
^It can be obtained as low as ³ and is comparable to commercially available foams of the same type. Similar to the case of Example 1, the results of examining the relationship between the dilution ratio of the wood material in the wood solution and the physical properties of the foam are shown in FIGS. 8, 9 and 10. As is clear from these figures, the density, compressive stress and elastic modulus are all closely related to the content of the wood solution, and are lowest at the content of 20 to 30%. It is considered that this is because when the content of the wood component is lower than the numerical value in the above range, the shape is not sufficiently retained when the foam is formed, and the foam once formed is shrunk and the density is increased. The higher the density, the higher the compressive strength and elastic modulus. This also shows that the presence of the wood solution is deeply involved in the foam formation.

2.2 Method using freon Alternatively, freon was used as a blowing agent instead of water in an aqueous solution of triethylenediamine, and a foam was obtained in the same manner as in 2.1.

This foam was a hard foam with fine and uniform closed cells, and exhibited excellent properties in that it did not undergo compressive deformation even when a load of 1 kgf was applied. Also in this case, as in 2.1, it was found that the content of the woody material in the wood solution and the physical properties (density, compressive stress and elastic modulus) of the obtained woody foam are closely related (respectively, (Figs. 11, 12, 13).

The physical properties of the representative wood-based foams of the present invention obtained in each of the above Examples are shown in Table 3 in comparison with those of commercially available polyurethane foams.

From Table 3, it can be seen that the foam prepared by the method of the present invention has substantially the same physical properties as the commercially available foam.

From the above description, it is understood that according to the method of the present invention, a wood-based foam having excellent physical properties, in which the wood component is actively involved in the formation of the foam resin, can be obtained. Therefore,
Wood components and PE in wood solution for physical properties of molded foam
The influence of the mixing ratio with G was examined by the method described in the following test examples.

Test Example 1 Wood solutions having different mixing ratios of wood material and PEG600 were prepared in the same manner as in Production Example 1 except that 5, 10, 15 and 20 g of PEG600 were used, respectively. These wood solutions were subjected to ring-opening polymerization of ε-caprolactone as described in Example 2, followed by foam molding. The physical properties of the molded foams, that is, density, compressive stress, and elastic modulus were compared and examined. Results 14th, 15th,
Shown in Figure 16. From these figures, it can be seen that the higher the wood content, the lower the density of the foam, and the lower the stress and compressive elastic modulus that cause 25% compressive deformation. That is, the higher the content of wood in the form of a wood solution, the higher the porosity and the relatively more soft foam-like properties. A soft foam having good physical properties can be obtained even by using a wood solution having an overwhelmingly large amount of wood material, with a weight ratio of wood material: PEG600 of 20: 5. As can be seen from the above results, according to the method of the present invention, since the wood material itself can be actively involved in the formation of the foam, even from a wood solution containing a wood material several times as much as polyethylene glycol. Thus, it is possible to obtain a flexible foam having a very large porosity, flexibility and excellent physical properties.

[Brief description of drawings]

FIG. 1 is an IR spectrum of a wood solution prepared in the presence (A) and absence (B) of maleic anhydride, and FIG. 2 is a wood solution and propylene oxide or ε-captolactone polyadded thereto. A graph showing the GPC chart (differential refractometer) of the thing, Fig. 3 is the GP of the same sample as Fig. 2.
Graph showing C chart (UV detector), 4, 5, 6,
Fig. 7 shows the density, compressive stress, elastic modulus, and yield stress of the wood-based foam prepared from the hydroxypropylated wood solution, and the dilution ratio of the wood material in the wood solution (wood solution (g)) / (wood Graphs showing the relationship with the solution (g) + propylene oxide (g)), FIGS.
-The density of a wood-based foam prepared with triethylenediamine from a wood solution that has been polyadded with caprolactone,
Graphs showing the relationship between compressive stress and elastic modulus and the dilution rate of wood in a wood solution, FIGS. 11, 12, and 13 are prepared using Freon from a wood solution to which ε-captolactone was polyadded. Graph showing the relationship between the density, compressive stress and elastic modulus of the wood-based foam, and the dilution ratio of the wood material in the wood solution, No. 1
4, 15, and 16 are graphs showing the relationship between the density, compressive stress, and elastic modulus of the wood-based foam, and the wood material content (mixing ratio of wood material and PEG600) in the wood solution.

Claims (4)

[Claims] 1. A wood solution obtained by dissolving a wood material in an organic solvent having an active group capable of polymerizing in the presence of an anhydride of a dibasic acid, a crosslinking agent or a curing agent, and if necessary, a foaming agent. A method for producing a wood-based foam, which comprises adding and curing the foam. 2. The method according to claim 1, wherein the anhydride of dibasic acid is dicarboxylic acid anhydride. 3. The method according to claim 1, wherein the organic solvent having an active group capable of polymerizing is selected from alcohols, phenols, ethers and ketones. . 4. The compound according to claim 1, wherein the dibasic acid anhydride is maleic anhydride or phthalic anhydride, and the organic solvent having an active group capable of polymerizing is a polyhydric alcohol. The method according to item 1.