JP2801740B2 - Method for producing flexible vegetable fiberboard - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention has a woody or plant-like appearance, has flexibility, can be used on a curved surface, or has a shock absorbing property. The present invention relates to a method for producing a flexible vegetable fiberboard which has properties and can be used as a cushion material for floors and the like.

[Conventional technology]

Plate materials that use vegetable fiber as the main raw material have been conventionally produced as insulation boards, hardboards, and MDFs.
It is used as an automobile member, floor material, and the like. But,
These vegetable fiber boards use wood fiber as the main raw material, so they are easy to obtain and have the advantage of being economically inexpensive, but use formaldehyde-based condensation resin as their binder. Therefore, there is no flexibility, it is difficult to use it on a curved surface, and it has poor shock absorption, so that it has a problem in use as a cushion material for floors and the like.

On the other hand, there is a cork board as a flexible vegetable board material, and a plate-like material obtained by joining granular cork, but since it is a limited natural product, it is difficult to obtain a large amount of raw materials, and there is also an economic problem. There are problems with widespread use.

In order to solve such problems, synthetic rubber latex is mixed with wood fiber, dried, then collected in a mat form, heated and pressed to produce a flexible fiberboard, rice and / or rice.
Or a product obtained by adding a vulcanizing agent to a synthetic rubber latex as a main ingredient in a piece of straw, wood chips, cork grains, rice husk, or the like,
Also disclosed are techniques such as a method of manufacturing a board for use as a flooring material having a cushioning property by bonding a material obtained by adding a vulcanizing agent to a synthetic rubber latex as a main component and further adding an amino resin to a binder. I have.

However, these methods still have problems in the production of a fiberboard that is truly flexible and shock-absorbing and a fiberboard that retains flexibility and shock-absorbing properties and has sufficient durability.

That is, in the former method, the binder used is described only as a synthetic rubber latex, but as described later, not all types of synthetic rubber latex provide sufficient flexibility, and the synthetic rubber latex is not used. When used alone, it has poor water resistance and lacks durability in an environment exposed to humidity and moisture. In the latter method, vulcanization is performed or an amino resin is added, so that the binder itself becomes hard, and it is difficult to obtain sufficient flexibility with all types of synthetic rubber latex.

[Problems to be solved by the invention]

An object of the present invention is to produce a fiberboard by a simple method using inexpensive vegetable fiber, and further have sufficient flexibility and, if necessary, water resistance and durability. The purpose is to produce a fiberboard that has both.

[Means for solving the problem]

The present invention has a main glass transition point after drying and curing from -20 ° C.
An aqueous emulsion of the composition at 10 ° C. was mixed with 4 to 40 parts by weight as a solid content based on 100 parts by weight of the dry weight of the vegetable fiber, and the water content after mixing was adjusted to 20% by weight or less. A method for producing a flexible vegetable fiberboard, which comprises laminating afterwards, and pressing and molding a laminated mat.

The plant fiber referred to in the present invention is a wood fiber obtained by fibrillating, pulverizing, cutting, or polishing wood and / or a fiber obtained by fibrillating, pulverizing, or cutting a stem or a seed shell of a monocotyledon. Of 1
It is desirable that the composition contains at least 80% by weight of a seed or a mixture of two or more kinds. In addition, it may contain fine cork particles, organic or inorganic foams, natural fibers such as cotton, wool, silk, and synthetic fibers. Absent.

The aqueous emulsion having a main glass transition point of −20 ° C. to 10 ° C. as referred to in the present invention is a monomer which copolymerizes with conjugated dienes such as butadiene and isoprene, for example, styrene.
Latex, natural rubber latex, chloroprene latex, butyl rubber latex, acrylic resin emulsion, ethylene vinyl acetate copolymer emulsion, polyvinyl acetate emulsion, copolymerized latex of various vinyl monomers such as methyl methacrylate and acrylonitrile,
Alternatively, carboxyl groups, N-
At least one reactive monomer having at least one crosslinkable reactive group such as a methylol group, an N-alkoxymethyl group, a glycidyl group, a β-methylglycidyl group, a hydroxyl group, an amino group, and an acid anhydride in a side chain; A mixture of one or more polymers, such as so-called modified latex, which has been polymerized and whose main glass transition point is from -20 ° C to 10 ° C.
° C, preferably -10 ° C to 5 ° C, more preferably -5 ° C to 5 ° C. Glass transition point is-
When the temperature is lower than 20 ° C., when the aqueous emulsion is mixed with the vegetable fiber and then sprinkled and laminated, the fibers tend to adhere to each other, and the thickness and density after the spraying are not uniform, and a stable quality fiberboard is obtained. Is a problem. On the other hand, when the glass transition point exceeds 10 ° C., the flexibility of the obtained fiberboard becomes insufficient at ordinary temperatures, and the object of the present invention cannot be satisfied. As long as the glass transition point satisfies the above range, the aqueous emulsion is a water-soluble polymer compound such as polyvinyl alcohol, a cellulose derivative, or a starch derivative, flour,
A filler such as an inorganic powder may be contained.

The fiberboard using only the above-mentioned aqueous emulsion as a binder has sufficient flexibility and practical strength under normal conditions, but when used in a humid atmosphere or in applications where it is exposed to water, it is water resistant. There's a problem. As a method for improving the water resistance of the fiberboard used for such a purpose, denaturation with an isocyanate compound is desirable. The amount of the isocyanate compound added is not particularly limited, but even in the case of performing denaturation with the isocyanate compound, the main glass transition point after drying and curing of the mixture of the aqueous emulsion and the isocyanate compound is required to obtain a flexible fiberboard. It is necessary to adjust the types and ratios of the aqueous emulsion and the isocyanate compound so that the temperature is from −20 ° C. to 10 ° C.

An isocyanate compound is a compound having two or more isocyanate groups in a molecule, for example, tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), xylene diisocyanate (XDI ), Isophorone diisocyanate (IPDI) and polymethylene polyphenyl polyisocyanate (polymeric MDI). In addition, a mixture of these isocyanate compounds and a polyol, or a so-called prepolymer which is polymerized in advance with an excess of isocyanate and polyol and has an isocyanate group remaining can also be used.

Since isocyanate compounds are generally not water-soluble, they may interfere with uniform mixing with an aqueous emulsion. In such a case, a method of dispersing using a surfactant may be employed, but in order to easily and uniformly disperse and mix, a compound obtained by adding an alkylene oxide to a monofunctional alcohol is allowed to act on an isocyanate compound to easily emulsify. Most preferred is a method using an isocyanate compound which has been rendered neutral. In order to impart sufficient emulsifiability, the molecular weight of the monofunctional alcohol is preferably 100 or less, and the number of alkylene oxides added is preferably 10 or more.

In addition, when conveying or compressing vegetable fibers mixed with an aqueous emulsion, when coating or a release agent is applied so that the inner surface of the pipe or the pressed surface has a low energy interface, there is not much problem, If such treatment is not performed, vegetable fibers mixed with the aqueous emulsion will adhere to the inner surface of the pipe and the press surface, and stable production,
This hinders the production of fiberboard with uniform physical properties. The coating or release agent application treatment has a problem in the persistence of the effect, and requires frequent treatment. The use of a phosphate mixture of a polyoxyalkylene monoalkyl allyl ether and / or a polyoxyalkylene monoalkyl ether and / or a polyoxyalkylene monofatty acid ether having an HLB value of 6 or more mixed with an aqueous emulsion allows use of such an adhesion. The problem can be solved. If the HLB value is less than 6, a problem may occur in mixing with the aqueous emulsion, or the effect of preventing adhesion is reduced. The addition rate is preferably 10% by weight or less based on the solid content of the aqueous emulsion.

The mixing ratio of the aqueous emulsion to the vegetable fiber is
The solid content is 4 to 40 parts by weight based on 100 parts by weight of the dry weight of the vegetable fiber. If the amount is less than 4 parts by weight, the strength of the obtained fiberboard will not be sufficient. If the content exceeds 40% by weight, the fibers tend to adhere to each other when the vegetable fiber is mixed with the aqueous emulsion and then sprayed and laminated, and the thickness and density after spraying are not uniform and stable on a uniform outer surface. There is a problem in obtaining a fiberboard of a proper quality.

The method of mixing the vegetable fiber and the aqueous emulsion is not particularly limited, but it is necessary to adjust the water content after mixing so as to be 20% by weight or less before laminating. If the water content exceeds 20% by weight, the fibers tend to adhere to each other when scattered and laminated, and not only the same problem as described above occurs, but also water remains between the fiberboard layers in the subsequent pressing operation. ,
In the case of lowering the adhesive strength and heating and pressing, a phenomenon called so-called puncturing, which breaks the adhesive layer when the vaporized moisture volatilizes between the fiberboard layers upon decompression, is likely to occur.

The pressing method at the time of molding is not particularly limited. However, in the aqueous emulsion of the present invention, the adhesive action is caused by evaporation of excess water and, when an isocyanate compound is mixed, an isocyanate group and an aqueous emulsion and / or a plant. Expressed by the reaction with the quality fiber. Therefore, in consideration of productivity, it is desirable to promote the evaporation of excess moisture by heating and, when mixing an isocyanate compound, the reaction between the isocyanate group and the aqueous emulsion and / or vegetable fiber. The heating and pressing conditions are:
Desirable heating temperature is 70 ~ 200 ℃, initial pressure is 2 ~ 8N / mm
^2, and the center layer temperature of the platelet during heating it is further desirable to reduce the pressure to 0.2~1.8N / mm ² as it becomes 70 to 100 ° C.. If the heating temperature is lower than 70 ° C., no improvement in productivity can be expected, and if the heating temperature is 200 ° C. or higher, so-called puncturing tends to occur. When the initial pressure is ² to 8 N / mm2 and the material is compressed as quickly as possible to a predetermined thickness, and when the temperature of the center layer of the plate-like material becomes 70 to 100 ° C and the water content of the fiberboard becomes easy to volatilize, the thickness becomes a predetermined value. The productivity is expected to be improved by reducing the pressure to 0.2 to 1.8 N / mm ² within the range not to exceed, and making it easy to remove outside the plate.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. still,
Parts and% in Reference Examples and Examples represent parts by weight and% by weight, respectively.

Reference Example 1 (Preparation of emulsifying isocyanate) 219.0 parts of diethylene glycol monomethyl ether and 4.45 parts of potassium hydroxide were placed in an autoclave, and after purging with nitrogen gas, the temperature was raised to 90 ° C, and 1052 parts of ethylene oxide were reacted under pressure, and propylene oxide was further added. 211.4 parts were reacted. The reaction product was neutralized with a theoretical amount of phosphoric acid and filtered. Put 25 parts of the obtained compound in a reaction vessel, add 1000 parts of CR-300 (crude diphenylmethane diisocyanate, manufactured by Mitsui Toatsu Chemicals, Inc.) at room temperature under a nitrogen stream and mix.
The mixture was reacted at 80 ° C. for 2 hours to obtain an easily emulsifiable isocyanate compound.

Reference Example-2 (Preparation of release agent) Emulgen 404 (polyoxyethylene monooleyl ether, HLB value: 8.8, manufactured by Kao Atlas Co., Ltd.) was heated to 70 ° C under a nitrogen stream in 2000 parts and 430 parts of phosphorus pentoxide was stirred. Was slowly added and reacted at 100 ° C. for 3 hours to obtain a phosphoric ester.

Example 1 200 parts of SMBR-based latex (non-volatile content: 45%) having a glass transition point of -4 ° C are uniformly sprayed on 1500 parts of steamed and mechanically defibrated Rawan-based wood fiber having a water content of 50%. It was applied and dried to a water content of 15%. 400 g of the fiber coated with the binder was deposited in a 30 cm square box so as to have a uniform thickness.
And pressing 2 min in ² pressure, to give a thickness 5 mm, the fiber board of a density 0.79 g / cm ³ by pressing after which the pressure in 1N / mm ² 3 minutes.

The impact absorption energy of this fiberboard according to the method specified in JIS-Z-2116 is 48 kgf · cm / cm ² , and the minimum bending radius is 6
It was 0 mm.

Example 2 For 1500 parts of the same Lauan wood fiber as in Example 1,
200 parts of SMBR latex (non-volatile content: 45%) and Reference Example-1
A mixture obtained by uniformly mixing 20 parts of the easily emulsified isocyanate compound obtained in (the main glass transition point after film formation of the mixture was 1 ° C.) was sprayed immediately after mixing, and the water content was increased to 10%. Dried to become. The fibers 400g of binder was applied, was deposited to uniformly become thick in box 30cm square, and pressing for 5 minutes at hot plate temperature 170 ° C. of the press, the thickness 5 mm, the fiber density of 0.78 g / cm ³ I got a board. The impact absorption energy of this fiberboard was 46 kgf · cm / cm ² , and the minimum bending radius was 68 mm.

Examples -3 to 9 / Comparative Examples -1 to 4 Fiberboards were produced and evaluated in a similar manner to Examples 1 and 2. The conditions and results are summarized in Table 1.

[Effects of the Invention] It is clear that the present invention makes it possible to produce a flexible and, if necessary, water-resistant vegetable fiberboard by a simple method without lowering workability.

Claims (7)

(57) [Claims] The main glass transition point after drying and curing is from -20 ° C.
An aqueous emulsion of the composition at 10 ° C. was mixed with 4 to 40 parts by weight as a solid content based on 100 parts by weight of the dry weight of the vegetable fiber, and the water content after mixing was adjusted to 20% by weight or less. A method for producing a flexible vegetable fiberboard, comprising laminating the laminate and pressing the laminated mat to form the laminate. 2. An aqueous emulsion comprising a mixture containing an aqueous emulsion and an isocyanate compound as main components and having a main glass transition point of -20 ° C. to 10 ° C. after drying and curing of the mixture. A) a method for producing a flexible vegetable fiberboard; 3. The flexible vegetable fiber board according to claim 2, wherein the isocyanate compound is a compound obtained by adding a compound obtained by adding an alkylene oxide to a monofunctional alcohol to make the isocyanate compound easier to emulsify. Production method. 4. The method according to claim 1, wherein the aqueous emulsion is one or a mixture of two or more of synthetic rubber latex and / or natural rubber latex and / or acrylic emulsion. A method for producing a flexible vegetable fiberboard according to the above. 5. An aqueous emulsion containing a phosphoric ester of a polyoxyalkylene monoalkyl ether and / or a polyoxyalkylene monoalkyl allyl ether and / or a polyoxyalkylene monofatty acid ether having an HLB value of 6 or more. The method for producing a flexible vegetable fiberboard according to any one of the above (1) to (4). 6. The plant fiber is one of wood fiber obtained by fibrillating, pulverizing or cutting wood and / or fiber obtained by fibrillating, pulverizing or cutting monocotyledon stem or seed shell. Alternatively, the method for producing a flexible vegetable fiberboard according to any one of claims (1) to (5), comprising at least 80% by weight of a mixture of two or more kinds. 7. A pressure-tightening heating temperature of 70 to 200 ° C., an initial pressure of ² to 8 N / mm ² , and a temperature at which the central layer temperature of the plate-like material being heated reaches 70 to 100 ° C. Pressure 0.2-1.8N / mm ²
The method for producing a flexible vegetable fiberboard according to any one of claims (1) to (6), characterized in that: