JPS5863435A - Manufacture of particle board - Google Patents

Abstract

PURPOSE:To provide a titled board which improves bending strength, and peeling resistance, by a method wherein a mat moisture content of a surface layer and a back surface layer before molding is maintained at a specified value, organic polyisocyanate is coated as a binder, and they are laminated and hot-pressed. CONSTITUTION:With respective to abolute dry chip, preferably 2-10% organic polyisocyanate (preferably crude disphenylmethanedisocyanate into which an anylin-formaldehyde condensate is phosgenized) is applied as a binder to a board surface and a board back layer in which a mat moisture content is kept to 20wt% or more. The surface layer and the back surface layer are laminated through the medium of a core layer which said binder is coated, where necessary, and a mat moisture content is maintained at preferably 10% or more, the lamination is molded by hot-press, thereby obtaining the desired board.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing particle board with improved thickness expansion upon water absorption.

Conventional particle board manufacturing methods use urea resins, melamine resins, phenolic resins, etc. as binders, and reduce the moisture content of the mat to 10 to 15 FIL% before hot-press molding.
Generally, it is kept at .

However, the prior art has a technical drawback in that the particle board expands greatly in thickness when it absorbs water, and an improvement has been needed.

The object of the present invention is to reduce this thickness expansion upon water absorption.

In order to achieve this object, the present inventor has arrived at the present invention as a result of various studies.

That is, the present invention is a method for producing particle board characterized by using an organic polyisocyanate as a binder and maintaining the moisture content of the mat at least 20% by weight or more in the front and back layers before hot-pressure molding (hereinafter, "H" is a special mention). (Unless otherwise specified, all weight percentages are expressed as % by weight).

In the present invention, the moisture content of the mat before hot-press molding refers to the moisture content of the chip after the binder has been applied and before it is inserted into the hot press, expressed as a percentage by weight of the absolutely dry chip. , 9 is simply expressed as matte moisture content.

The organic polyinsyanate referred to in the present invention is a compound having at least two -Nco groups in the molecule. Typical examples include aliphatic incyanates such as hexamethylene diinocyanate), m-Also Fi, p-phenylene diisocyanate, tolylene-2,4- or -2,6
-diisocyanate, diphenylmethane-4,4'-cyinoaanate, chlorphenylene-2,4-cyynonanate, naphthylene-1,5-diisocyanate, diphenylene-4,4'-diisocyanate, 4,4'-
diisocyanate) -3,3'-dimethyldiphenyl,
Aromatic incyanates such as 3-methyl-diphenylmethane-4,4'-diisocyanate and diphenyl ether diisocyanate, cyclohexyl-2,4- or -2,6-diincyanate and mixtures thereof and bis-(iso7anate cyclohexyl )-cycloaliphatic diisocyanates such as methane), 2,4.6-) diincyanate toluene, and triisocyanates such as 2,4.4'-) diincyanate diphenyl ether. Also mixtures of various incyanates, such as mixtures of tolylene diisocyanate isomers, such as 2,4- and 2,6-
There are commercially available mixtures of isomers as well as mixtures of difunctional, trifunctional or higher functional polyisocyanates prepared by phosgenation of aniline/formaldehyde condensates.

Crude phosgenation products containing ane7to are included, which contain diisocyanates, triisocyanates, and higher polyisocyanates as well as any phosgenation by-products.

In addition, NCO-terminated prepolymers prepared by prepolymerizing polyols such as polyethylene glycol and polypropylene glycol with an excess of the above-mentioned polyincyanate, or OH-terminated prepolymers obtained by prepolymerizing the above-mentioned polyisocyanate with an excess of polyol, and polyiso-7 such as diphenylmethane diisocyanate are used. It also includes those obtained by adding and reacting an excessive amount of anate.

Also included are products obtained by reacting a compound obtained by adding ethylene oxide or ethylene oxide and propylene oxide to a monofunctional alcohol on the polyisocyanate.

In short, all compounds having two or more -Neo groups in the molecule on average are applicable, and of course, a mixture of two or more of these may be used.

Cheap tolylene-2,4- or -2,6-diisocyanate and mixtures thereof, diphenylmethane-4,4'
- Diisocyanates, bifunctional or trifunctional monomers prepared by phosgenation of aniline/formaldehyde condensates
There are products obtained by reacting a mixture of higher polyisocyanates or a compound obtained by adding ethylene oxide or ethylene oxide and propylene oxide to a monofunctional alcohol on this mixture.

Examples of polyisocyanates that are currently suitable include polyisocyanates that are liquid at room temperature and have a relatively low vapor pressure and are easy to handle; difunctional or trifunctional or higher polyisocyanates produced by phosgenation of aniline/formaldehyde condensates; Examples include products obtained by reacting a mixture of isocyanates or a mixture thereof with a compound obtained by adding ethylene oxide or ethylene oxide and propylene oxide to a monofunctional alcohol.

In the present invention, the moisture content of the mat must be at least 20 inches for the front and back layers, and if it is less than 20 inches, the thickness expansion of the particle board upon water absorption will not be sufficiently improved.

Particleboard can have a single-layer structure or a multi-layer structure, but in the case of a multi-layer structure, it is essential to maintain the mat moisture content of the front and back layers, which increase the density, at 20 cm or more. It is also desirable that the moisture content of the matte layer (all layers other than the front and back layers) is high, and specifically, 10 inches or more is desirable. Further, it is preferable that the moisture content of the mat does not exceed 40% for both the front and back layers, and 30% for the middle layer, from the standpoint of maintaining other physical properties such as bending strength and peel strength, and preventing banks.

The adhesive used in the present invention must be an organic polyisocyanate, and conventional resins such as urea formaldehyde resin, melamine formaldehyde resin, urea melamine formaldehyde resin, phenol formaldehyde resin, melamine phenol formaldehyde resin, etc. are used in the method of the present invention. However, this is not practical because problems such as a significant decrease in the performance of the board and a significant lengthening of the hot pressing time during board production occur.

Next, the amount of the organic polyisocyanate of the present invention applied to the wood chips must be 1% or more based on the absolute dry amount thereof, and is preferably in the range of 2 to 10 inches. If this value is less than 1%, the performance of the tickle board is not sufficient;
If it exceeds 0%, it is not possible to expect much improvement in performance commensurate with the amount used.

According to the method of the present invention, the thickness expansion of the tickle board upon absorption of water can be reduced from about 10 inches in the prior art to 5 inches or less, which is a significant improvement. However, this is a point that conventional technology has not been able to overcome.

Furthermore, it has been found that the method of the present invention not only improves the thickness expansion upon water absorption but also improves board performance such as bending strength and peel strength.

As described above, the present invention has high practical value.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these in any way.

In the following, parts are by weight unless otherwise specified.

Example 1 Water was sprayed in advance on chips with a moisture content of 5 inches.
Apply 7 parts by weight of t-200 (crude diphenylmethane diisocyanate manufactured by Mitsui Toatsu Chemical Co., Ltd.) using a conventional method, and the spraying ratio of resin to the weight of the bone dry chip is 96 inches),
Heat pressure temperature 170℃, heat pressure time 6m1n, clamping pressure 50K
gf/cdl, board thickness 16 mm, board density o, 7
It was molded into fArit. The performance of the board was evaluated using the method specified in J.E. 5A-5908, and the results were as follows.

Water absorption thickness expansion rate 5.5 inches Bending strength 240/Cr11 Peeling strength 15. OKff/cd Example 2 Chips with a moisture content of 25 chips (hereinafter referred to as chips A) 10
Apply 7 parts by weight of TD Any 8020 (a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate at SO/2O (weight ratio)) to 0 parts by weight using a conventional method and reduce the weight of the bone dry chip. The above TDI-80
/20 is applied in an order of 5 parts by weight, and the spraying ratio of cloudy fat is 5.7% based on the weight of the bone dry chip), and the weight ratio after resin application is A:B:A in the order of chip A1 chip B1 chip A. =1:
Forming so that the ratio is 3:1, hot pressure temperature 150℃, hot pressure time 10m1n, compaction pressure 30kpfA! i = board thickness 1
6IT1/rr11 average void density 065 f/, -. The performance of the board was evaluated using the method specified in J.Eng.SA-5908, and the results were as follows.

Water absorption thickness expansion rate 67% Bending strength 257/cl = Peeling strength
12.5 ratio f/i Example 3 2190 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 then 1052 parts of ethylene oxide was reacted under pressure. , and further reacted with 2114 parts of propylene oxide. Thereafter, the reaction product was neutralized with a stoichiometric amount of cynic acid and made into a sintered product. (Hereinafter, this product is abbreviated as A-1) 25 parts of this compound A-1 was charged into a reaction vessel, and 1000 parts of MDI=
OR-20, (l (crude diphenylmethane diisocyanate manufactured by Mitsui Toatsu Chemical Co., Ltd.) was charged and mixed, the internal temperature of the reaction vessel was raised to 80°C, and the mixture was stirred at 80°C for 2 hours. The reactant (hereinafter abbreviated as Al-1) had a viscosity of 195 centipoise (25°C).This compound Al-1 was dispersed in water to a concentration of 20% and added to 100 parts by weight of chips with a water content of 3. (12 parts by weight of the above Al-1 dispersion was applied, and the resin spraying rate was 2.5% based on the weight of the bone-dry chip.) Heat pressure temperature: 170°C, heat pressure time: 6
The board was molded to a thickness of 13 ny'fn and a board density of 0.7 f/crA using a pressing pressure of 3 ON and A-. , Tl5A
The performance of the board was evaluated using the method stipulated in -59C18, and the results were as follows.

Water absorption thickness expansion rate 59 cm Bending strength 256 Kgf/crl Peeling strength 1o, s Kyf/cdl comparative example 1
' According to a conventional method, urea resin liquid for particle board (Mitsui Toatsu Chemical Co., Ltd. U-755) was added to 100 parts by weight of the chips with a moisture content of 5% used in Example 1.
Apply 12 parts by weight of a sizing solution made by blending 30 parts by weight of water and 1 part by weight of ammonium chloride to 100"M parts (non-volatile content: 65 cm), so the matte moisture content is approximately 12 cm). Heat pressure temperature: 170
The board was molded to a board thickness of 13 m/m and a board density of 0.7 fI/cd at a temperature of 6 min at a temperature of 6 min and a clamping pressure of 50 Ky'aA. The performance of the board was as follows.

Water absorption thickness expansion rate N, 5 inches Bending strength 206 Kg/d Peeling strength
15.3 Kg/cn In this way, the thickness expansion upon absorption of water is significantly inferior to the board of Example 1.

In Comparative Example 2, 10 parts by weight of the urea resin liquid for particle board used in Comparative Example 1 was applied to 109 parts by weight of the chip, and molding was attempted under the conditions of Example 1, but the board failed due to puncture. Since there was no mold, the hot pressing time was extended to 12 ml and molded.

The board performance was as follows.

Water absorption thickness expansion rate 99° Curved strength 115° Peeling strength 2. I Ky'cr/1 As can be seen, the board of Example 1 is significantly inferior to the board of Example 1 in terms of thickness expansion upon water absorption, bending strength, and peel strength.

Comparative Example 3 For chips under the same conditions as Example 2, a phenolic resin for particle board (PL-2 manufactured by Mitsui Toatsu Chemical Co., Ltd.) was used.
I applied the same amount (80% non-volatile content: 45%) and tried molding under the same conditions, but a puncture occurred and the board could not be manufactured. Although the hot pressing time was further extended to 20 ml, it was still impossible to form a plate.

Therefore, the chips of Example 2 were dried in advance, and the chips with a moisture content of 25 inches were dried with a moisture content of 4%, and the chips with a moisture content of 12 inches were dried with a moisture content of 2%.
It was hot. (The chip with a moisture content of 4% is hereinafter referred to as Chip A', and the chip with a moisture content of 2% is hereinafter referred to as Chip B'.) 20 parts by weight of the above phenol resin is applied to 100 parts by weight of the chip, and the chip is reduced to 100 parts by weight. 12 parts by weight of the above phenol resin was applied to chip A', chip B', and chip A.
'The weight ratio after resin application is X:B':A'=1:
Forming was carried out so that the ratio was 3:1, and molding was carried out under the same conditions as in Example 2. The results of evaluating the board performance were as follows.

Water absorption thickness expansion rate 95cm Bending strength 236K@'7 Peeling strength
8.8 Kg/cfII The performance of this phenol board is quite satisfactory when compared to the standard of conventional particle boards, but it is inferior when compared to the board of Example 2.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] Organic polyisocyanate is used as a binder, and the moisture content of the mat before hot-pressing is reduced to 20% for both the front and back layers.
A manufacturing method of toss particle board characterized by keeping above weight%.