JP2001200500A - Fiber plate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber plate having a sufficient strength without greatly changing electric charge balance of fiber dispersion even if white water is repeatedly used by using a specific enhancer in producing the fiber plate from a water dispersion of vegetable fiber. SOLUTION: An enhancer comprises an amphoteric polymer composed of 1-40 mol% of a cationic vinyl monomer of formula (1) (R1 and R2 are each independently hydrogen or methyl; HX is an acid), 40-98 mol% of (meth) acrylamide and 1-25 mol% anionic vinyl monomer selected from an α,β-unsaturated carboxylic acid and its salt as essential components. This fiber plate comprises a vegetable fiber and the amphoteric polymer. The fiber plate is produced by adding the amphoteric polymer to a water dispersion containing the vegetable fiber and molding. The electric charge balance of the fiber dispersion is not greatly changed even if white water is repeatedly used for dispersion of the vegetable fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fiberboard and a method for producing the same.

[0002]

2. Description of the Related Art A fiberboard manufactured by a wet method using vegetable fibers such as wood fibers (pulp) as a main raw material is also called an insulation board or the like, and generally has a thickness of 7 mm or more. In the production of fiberboard, vegetable fiber used as a raw material has a weak fiber entanglement and, as it is, lacks strength after board formation. Therefore, starch or a derivative thereof is generally widely used as an enhancer. However, since starch-based drugs have a low fixation rate to fibers, if they are used alone as an enhancer, the drainage load increases, and the drying efficiency in the wet mat drying step is poor, so the drying with a dryer is not possible. The residence time is prolonged, resulting in a reduced production speed of the fiberboard.

The use of cationic polyacrylamide has been proposed in order to compensate for the disadvantages of starch-based drugs, but general cationic polyacrylamide has poor fixation to fibers, and therefore can exhibit sufficient strength. Did not. This is considered to be due to the fact that a large amount of water-soluble lignin and hemicellulose-derived substances, which are polyanions, are present in the raw vegetable fiber, and neutralize cations in polyacrylamide to inhibit fixation to the fiber. . Also,
The cationic polyacrylamide, which has not been fixed in the fibers, is added to the vegetable fibers again together with the water (called “white water”) that is filtered off during the formation of the wet mat. Is changed to the percation side, and the yield of the fine fibers and the added chemicals in the fiber dispersion is further reduced. One way to improve the anchorage of cationic polyacrylamide is to increase the molecular weight. However,
When the molecular weight of polyacrylamide is increased, the cohesive strength is increased, and when added to vegetable fiber, a strong floc is generated, which causes a significant decrease in strength after board formation, so it was necessary to limit the amount of addition. .

On the other hand, JP-A-8-100400 proposes a method using a copolymer of a diallylamine monomer and (meth) acrylamide as a reinforcing agent for a fiberboard. The cationic copolymer disclosed in this publication has a good fixation rate to a fiberboard and enables production of a high-strength fiberboard, but when used in an amount sufficient to exert its effect, white water There is still a problem that the charge balance of the fiber dispersion is changed to the percation side during repeated use, and the yield of the fine fibers and the added chemicals in the dispersion is reduced.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the drainage load and to produce a fiberboard which has sufficient strength by using a relatively small amount of a reinforcing agent. Another object of the present invention is to produce a fiberboard having sufficient strength without significantly changing the charge balance of the fiber dispersion even when white water is repeatedly used.
The present inventors have conducted intensive studies to solve such a problem, and as a result, have found that excellent results can be obtained by using an amphoteric polymer obtained by copolymerizing a specific monomer at a specific ratio as an enhancer. Heading, and led to the present invention.

[0006]

That is, the present invention relates to a vegetable fiber and a compound of the formula (I)

[0007]

(Wherein R ¹ and R ² each independently represent hydrogen or methyl, and HX represents an acid) 1 to 40 mol% of a cationic vinyl monomer, and 40 to 98 mol% of (meth) acrylamide And an anionic vinyl monomer 1 selected from α, β-unsaturated carboxylic acids and salts thereof.
Provided is a fiberboard containing an amphoteric polymer having 25 mol% as an essential component. Furthermore, an aqueous dispersion containing vegetable fibers is provided,
An object of the present invention is to provide a method for producing a fiberboard by adding and molding the amphoteric polymer.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The cationic vinyl monomer of formula (I) is a salt of a secondary amine typified by diallylamine and di (2-isobutenyl) amine. Of these, diallylamine salts are preferably used. The acid constituting the salt represented by HX in the formula (I) may be an inorganic acid or an organic acid, and examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid,
Phosphoric acid and the like can be mentioned, and as the organic acid, acetic acid, formic acid, oxalic acid, propionic acid and the like can be mentioned. Generally, hydrochloric acid, sulfuric acid and the like are preferred. By mixing diallylamine or di (2-isobutenyl) amine with these acids, a cationic vinyl monomer (salt) of the formula (I) is formed. These cationic vinyl monomers may be used alone or in combination of two or more in copolymerization.

The (meth) acrylamide which is another essential component constituting the amphoteric polymer is acrylamide or methacrylamide, and among them, acrylamide is preferable.

Another essential component constituting the amphoteric polymer is an anionic vinyl monomer.
α, β-unsaturated carboxylic acids or salts thereof. This α,
β-unsaturated carboxylic acids include monocarboxylic acids such as acrylic acid and methacrylic acid, as well as maleic acid and fumaric acid,
It may be a polycarboxylic acid such as a dicarboxylic acid such as itaconic acid. Examples of the salt form include metal salts such as sodium salts and potassium salts, and ammonium salts. These anionic vinyl monomers also
Each can be used alone or in combination of two or more.

In producing the amphoteric polymer, the cationic vinyl monomer of the formula (I) is 1 to 40 mol%,
(Meth) acrylamide is used in a proportion of 40 to 98 mol%, and anionic vinyl monomer is used in a proportion of 1 to 25 mol%. Preferably, 5 to 30 mol% of the cationic vinyl monomer of the formula (I) and 50% of the (meth) acrylamide
~ 92 mol%, and the anionic vinyl monomer is 3 ~
It is used at a rate of 25 mol%. By using an amphoteric polymer obtained by copolymerizing each monomer at a specific ratio in this way, when blending it to produce a fiberboard, the charge balance of the fiber dispersion greatly changes even if white water is repeatedly used. Thus, a fiberboard having a sufficient strength can be manufactured.

In the amphoteric polymer, one or more kinds of other monomers copolymerizable therewith can be introduced while maintaining the ratio of the above essential components. When other monomers are introduced, they are usually used in a range of 40 mol% or less based on all monomers. Other monomers that can be optionally introduced include, for example, water-insoluble nonionic monomers such as (meth) acrylonitrile, methyl (meth) acrylate, hydroxyethyl (meth) acrylate, styrene and vinyl acetate, and dimethylaminoethyl. (Meth) acrylates and dimethylaminopropyl (meth) acrylamides or their quaternaries, cationic monomers such as dimethylamine and diallyldimethylammonium chloride, such as ethylene glycol di (meth) acrylate and methylenebis (meth) acrylamide And bifunctional monomers.

The amphoteric polymer used in the present invention can be obtained by copolymerization using the essential monomer components described above and, if necessary, any monomer components. The production of the amphoteric polymer can be carried out by a known method, and the type of polymerization is not limited. Is preferably performed. Conventional polymerization initiators can be used. For example, persulfates such as ammonium persulfate and potassium persulfate, 2,2'-diamidino-2,
Examples include azo compounds such as 2'-azodipropane dihydrochloride and azobisisobutyronitrile, and peroxides such as di-t-butyl peroxide, cumene hydroperoxide and hydrogen peroxide. Known redox initiators, for example, a combination of potassium persulfate and sodium bisulfite or a tertiary amine can also be used. Further, if necessary, known and commonly used chain transfer agents such as isopropyl alcohol and allyl alcohol can be used.

The polymerization is usually carried out at a temperature of 10 to 100 ° C., preferably 40 to 90 ° C., for about 1 to 20 hours. This polymerization can be performed in the presence of oxygen, but is preferably performed in an atmosphere of an inert gas such as nitrogen gas. In the polymerization, the essential components and a monomer copolymerizable with these essential components used as necessary may be used to initiate polymerization after charging all of these components collectively, or only certain components, or After the polymerization is started by charging only a part of all the components, the remaining components may be added continuously or dividedly to continue the polymerization.

Among the amphoteric polymers thus obtained,
The viscosity at 25 ° C. of the 15% by weight aqueous solution is 5%.
In the range of 00 to 20,000 mPa · s, especially 2.0
Those in the range of 00 to 10,000 mPa · s are preferred. If the viscosity is too low, the effect of increasing the strength of the fiberboard will not always be sufficient, while if the viscosity is too high, it will be difficult to handle the copolymer, and strong floc will occur when added to the vegetable fiber. This will cause the strength of the formed fiberboard to decrease.

The above amphoteric polymer is added to an aqueous dispersion of vegetable fibers, and a fiberboard is formed from the aqueous dispersion. The plant fiber used here can be various generally known ones, for example, wood fiber, plant fiber such as straw fiber or waste paper pulp fiber,
It is also possible to use a small amount of synthetic fibers in combination. The production of the fiberboard itself can be performed according to a usual wet method. That is, a fibrous board is obtained by preparing a wet mat from an aqueous dispersion containing a vegetable fiber and an amphoteric copolymer and drying. Then, a fiber wet mat is formed from this aqueous dispersion to form a fiberboard, and even if white water filtered off at the time of forming the wet mat is repeatedly used for dispersing the vegetable fiber, the aqueous dispersion of the vegetable fiber can be used. The fiberboard can be manufactured without greatly changing the charge balance of the fiberboard.

The amphoteric polymer is added in a range of usually 0.01 to 10 parts by weight, preferably 0.2 to 3 parts by weight as a solid content, based on 100 parts by weight of the dry weight of the fiber. If necessary, a sulfuric acid band, a sizing agent, a retention agent, and the like can be added to the vegetable fiber or the aqueous dispersion containing the copolymer. Furthermore, other enhancers such as starch-based drugs can be used in combination. The fiberboard after the drying step can be impregnated with an adhesive or a flame retardant, if necessary.

[0019]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The percentages and parts in the examples are by weight unless otherwise indicated.

Synthesis Example 1 58.5 g (0.2 mol) of a 50% diallylamine sulfate aqueous solution and 388.6 g of ion-exchanged water were charged into a reactor equipped with a stirrer, and the pH was adjusted to 2.0 with a trace amount of 71% sulfuric acid. did. Next, the air in the apparatus was sufficiently replaced with nitrogen gas to make it oxygen-free, and then ammonium persulfate 0.27 at 60 ° C.
g was added. Subsequently, while maintaining the internal temperature at 60 ° C.,
85.3 g (0.6 mol) of 8% aqueous acrylamide and 8%
18.0 g (0.2 mol) of a 0% aqueous solution of acrylic acid was added to the reaction system over 5 hours. Thereafter, the reaction was completed by keeping the temperature at 60 ° C. for 2 hours to obtain an aqueous solution of amphoteric polyacrylamide. The product has a polymer content of about 15% and a pH of 2.
Brookfield viscosity at 0,25 ° C. is 5,30
It was 0 mPa · s.

Synthesis Examples 2 and 3 and Comparative Synthesis Example Polymerization was carried out in the same manner as in Synthesis Example 1 except that the composition of the monomers constituting the copolymer was changed as shown in Table 1.
The amount of ammonium persulfate for controlling the viscosity was appropriately changed each time.

[0022]

TABLE 1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example No. Shi Bu allylamine sulfate Akuriruamito Bu acrylate copolymerization Physical properties (mol%) (mol%) (mol%) Concentration (%) Viscosity (mPas) pH ━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━━ Synthesis example 1 20 60 20 15 5,300 2.0 〃 2 20 70 10 15 4,700 1.9 ３ 3 20 75 5 15 4,200 2.0 ──────────────例 Comparative Synthesis Example 20 80 − 15 5,500 2.1 ━━━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━

Examples 1 to 3 Wood fibers were mixed with fresh water at a concentration of 2% to prepare aqueous dispersions of wood fibers. To 100 parts of the fiber solid content, 0.3 part of a sulfuric acid band and 0.5 part of any of the amphoteric polyacrylamide aqueous solutions obtained in Synthesis Examples 1 to 3 were added in terms of solid content, and then the rosin emulsion size was reduced to 0%. .7 parts were added. This was separated by filtration by a wet method, and the obtained wet mat was pressed with a press, and then dried with a dryer at 120 ° C.
After drying for 20 minutes, a fiberboard having a thickness of 10 mm was prepared. For each fiberboard, the density, bending strength, water absorption and enhancer fixation were measured, and the results are shown in Table 2. The bending strength and water absorption were measured according to JIS A 5905. The fixing rate of the enhancer is determined by measuring the nitrogen content in the fiberboard by elemental analysis, and then using the enhancer (amphoteric polyacrylamide).
Was calculated by the following equation from the calculated fixing amount and the added amount.

Fixing rate of enhancer (%) = (fixed amount of enhancer / added amount of enhancer) × 100

Comparative Examples 1 to 3 In place of the copolymers obtained in the above Synthesis Examples 1 to 3, the following enhancers were used per 100 parts of the solid content of the fiber, and the following amounts were used. A fiberboard was prepared in the same manner as in No. 3.

Comparative Example 1: 5 parts of starch were added. Comparative Example 2: "Sumirez Resin EP-2" which is a 15% aqueous solution of a modified acrylamide / acrylic acid copolymer Mannich
2D ”(obtained from Sumitomo Chemical Co., Ltd.) in terms of solid content of 0.5
Parts added. Comparative Example 3: A 15% aqueous solution of the cationic polyacrylamide obtained in Comparative Synthesis Example 1 was added in an amount of 0.5 parts in terms of solid content.

Examples 1 to 3 for each fiberboard
The results were evaluated in the same manner as described above, and the results are shown in Table 2. The fixing amount of starch to the fiberboard in Comparative Example 1 was:
A small piece of the fiberboard was immersed in an aqueous glucoamylase solution, the starch was extracted in the form of glucose, and the amount of glucose was determined by a quantitative method.

Examples 4 to 6 and Comparative Examples 4 to 6 As experiments simulating actual industrial operation, Examples 1 to 6
Using the filtrate (white water) obtained in each of the filtration steps of Comparative Example 3 and Comparative Examples 1 to 3, wood fibers were mixed at a concentration of 2%, and a fiberboard was prepared in the same manner as before, and a similar fiberboard was prepared. The method was evaluated. The difference between the bending strength in each of these examples and the bending strength of a fiberboard obtained from an aqueous dispersion of wood fibers prepared using fresh water (bending strength difference = bending strength when using white water−when using fresh water) Bending strength) was calculated. The smaller the absolute value of this bending strength difference, the more stable the quality can be obtained even if white water is repeatedly used. Due to the deterioration of quality, it is not suitable for industrial operation. Table 2 also shows the results of these tests.

[0029]

[Table 2] Example No. Polymer used Density Bending strength Bending strength difference Water absorption Strengthening agent fixation rate (g / cm ³ ) (N / mm ² ) (N / mm ² ) (g / cm ³ ) (%) ━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━ Example 1 Synthesis Example 1 0.24 1.59-0.057 73.0 〃 2 Synthesis Example 2 0.25 1.67-0.051 74.5 〃 3 Synthesis Example 3 0.25 1.65 − 0.050 75.1 ──────────────────────────────────── Comparative Example 1 Starch 0.24 1.38 − 0.106 22.7 〃 2 Mannich modified product 0.24 1.39 − 0.088 34.9 ３ 3 Comparative synthesis example 0.25 1.73-0.042 76.3 例━━━━ Example 4 Synthesis Example 1 0.24 1.63 0.04 0.061 77.0 ５ 5 Synthesis Example 2 0.24 1.69 0.02 0.058 75.4 〃 6 Synthesis 3 0.24 1.64-0.01 0.055 76.2 ──────────────────────────────────── Comparative Example 4 Starch 0.25 1.47 0.09 0.102 26.3 ５ 5 Modified Mannich 0.23 1.38-0.01 0.093 34.2 〃 6 Comparative synthesis example 0.23 1.55-0.18 0.067 65.0 例━━━━━━━━━━

As can be seen from Table 2, in Comparative Example 1 using starch, the fixing rate of starch was low and sufficient strength could not be obtained. In addition, the water absorption is large, and the fixing of the sizing agent is not sufficient. The acrylamide / acrylic acid copolymer Mannich modified product used in Comparative Example 2 has a cationic group introduced into the acrylamide portion by the Mannich modification, and has an amphoteric polymer due to the presence of the acrylic acid unit. However, even if it is used, the fixing rate is low and sufficient strength cannot be obtained. On the other hand, in Comparative Example 3 using polyacrylamide in which a cationic group was introduced by diallylamine, the fixing rate of the polyacrylamide was high, and the strength was improved. In Comparative Example 6 using the white water, fresh water was used. The strength is lower than that of Comparative Example 3 used. Further, in Comparative Example 6, the fixing rate also tends to decrease as compared with Comparative Example 3.

On the other hand, in Examples 1 to 3 using a diallylamine / acrylamide / acrylic acid-based amphoteric polymer according to the present invention, the fixing rate is high and the strength is high. Also, in Examples 4 to 6 using these white waters, there is almost no decrease in strength and the fixing rate is good as compared with Examples 1 to 3 using the fresh water.

[0032]

According to the present invention, a fibrous board is prepared by applying a specific cationic vinyl monomer, (meth) acrylamide and an anionic vinyl monomer as essential components and applying an amphoteric polymer copolymerized at a specific ratio to a vegetable fiber. By manufacturing the above, even if white water is repeatedly used, the charge balance of the fiber dispersion liquid does not significantly fluctuate. Therefore, even in the continuous operation on an industrial scale, the amphoteric polymer acts as an augmenting agent having sufficient suitability, and a fiberboard having high strength can be produced. Also, since the fixing rate of the enhancer is high, the load of drainage can be reduced, and the fixing of other concomitant drugs such as sizing agents is enhanced,
The effect of these concomitant drugs can be promoted.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Yamamoto 3-1-198 Kasuganaka, Konohana-ku, Osaka-shi Within Sumitomo Chemical Co., Ltd. (72) Inventor Shigeto Makino 3 Kasuganaka, Konohana-ku, Osaka-shi No. 1-98 Sumitomo Chemical Industries Co., Ltd. (72) Inventor Makoto Kimuro 12 Shiodome-cho, Minato-ku, Nagoya Nichiha Stock Company In-house F-term (reference) 4L055 AA01 AA05 AG70 AG73 AH16 BD14

Claims (6)

[Claims] 1. A vegetable fiber and a compound of the formula (I) (Wherein, R ¹ and R ² each independently represent hydrogen or methyl, and HX represents an acid) 1 to 40 mol% of a cationic vinyl monomer represented by the following formula:
A fiberboard comprising an amphoteric polymer comprising 8 mol% and 1 to 25 mol% of an anionic vinyl monomer selected from α, β-unsaturated carboxylic acids and salts thereof as essential components. 2. The cationic vinyl monomer of the formula (I)
The fiberboard according to claim 1, which is a salt of diallylamine. 3. The amphoteric polymer comprises 5 to 30 mol% of a cationic vinyl monomer of the formula (I), 50 to 92 mol% of (meth) acrylamide and 3 to 2 anionic vinyl monomers.
3. The fiberboard according to claim 1, wherein 5 mol% is an essential component. 4. An aqueous dispersion containing a vegetable fiber, wherein (Wherein, R ¹ and R ² each independently represent hydrogen or methyl, and HX represents an acid) 1 to 40 mol% of a cationic vinyl monomer represented by the following formula:
A process for producing a fiberboard, comprising adding 8 mol% and 1 to 25 mol% of an anionic monomer selected from an α, β-unsaturated carboxylic acid and a salt thereof as an essential component, followed by molding. . 5. An amphoteric polymer is added to the aqueous dispersion, a fiber wet mat is formed from the dispersion to form a fiberboard, and the white water filtered off during the formation of the wet mat is removed from the vegetable fiber. The method according to claim 4, wherein the fiberboard is produced without repeatedly changing the charge balance of the aqueous dispersion by repeatedly using the dispersion of the aqueous dispersion. 6. The amphoteric polymer according to claim 1, wherein the dry weight of the plant fiber is 1.
6. The method according to claim 4, wherein 0.01 to 10 parts by weight is added to 00 parts.