JPH07119091A - Production of flame-retardant paper for paper honeycomb core - Google Patents

Abstract

PURPOSE:To provide a process for the production of a flame-retardant paper for paper honeycomb core, composed of an inorganic paper containing flame- retardant inorganic powder and having excellent flame-retardancy and compressive strength. CONSTITUTION:An inorganic paper containing 65-80wt.% of inorganic powder is impregnated with (1) 2-10wt.% (based on the bone-dry weight of the inorganic paper in terms of solid weight) of a synthetic resin having methylol group and (2) 100-200wt.% (based on the solid weight of the synthetic resin) of a guanidine-based flame-retardant produced by mixing sulfamic acid or phosphoric acid with cyanoguanidine and formaldehyde at molar ratios of 1:(1-1.5):(0.2-3). The impregnated inorganic paper is dried by heating to effect the crosslinking reaction of the methylol group in the synthetic resin and the crosslinking reaction of the synthetic resin with the guanidine-based flame-retardant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a flame-retardant paper as a base material for producing a paper honeycomb core,
More specifically, it relates to a method for producing a flame-retardant paper for a paper honeycomb core having excellent flame retardancy and compressive strength.

[0002]

BACKGROUND OF THE INVENTION Flame-retardant paper is widely used as a wall covering material, a building base material, a base material for electronic devices, etc., and also as a base material for making a paper honeycomb core. Such flame-retardant paper uses cellulose pulp as a fiber, paper obtained by applying a flame-retardant to paper obtained by papermaking with a paper machine, or a small amount of synthetic fiber or inorganic fiber in cellulose pulp as fiber. It is known that a raw material obtained by using a papermaking machine together with a raw material prepared by adding a flame-retardant organic substance or inorganic substance to the papermaking machine is used. A typical inorganic paper produced by mixing paper with flame-retardant inorganic powder together with fibers is an inorganic paper obtained by adding aluminum hydroxide powder as an inorganic powder to pulp fiber and mixing with paper. .

[0003]

However, such an inorganic paper contains an inorganic substance which imparts flame retardancy as a powder, and its content is high, and the content of pulp fibers constituting the paper is high. Since the amount is small, the strength of the paper is low. When a paper honeycomb core made of such an inorganic paper is used as a building base material, there is a problem that the compression strength and the impact resistance are inferior even though the flame retardancy is excellent.

A method for improving the compressive strength of a paper honeycomb core made of inorganic paper is disclosed in, for example, Japanese Patent Laid-Open No. 5-5.
In Japanese Patent No. 7825, it is proposed to impregnate a paper honeycomb core made of inorganic paper with water glass.
However, although this method improves the compressive strength, it requires an additional step of impregnating with water glass, which inevitably increases the manufacturing cost.

Therefore, an object of the present invention is to provide a method for producing a flame-retardant paper for a paper honeycomb core, which is made of an inorganic paper containing a highly flame-retardant inorganic powder, is excellent in flame retardancy, and has further improved compression strength. To provide.

[0006]

That is, a method for producing a flame-retardant paper for a paper honeycomb core according to the present invention comprises a fiber and a flame-retardant inorganic powder as a main component, and the inorganic powder per absolute dry weight. Inorganic paper containing 65-80% by weight,
(1) A synthetic resin having a methylol group in a solid content of 2 to 10% by weight based on the absolute dry weight of the inorganic paper, and (2) sulfamic acid or phosphoric acid, cyanoguanidine and formaldehyde in a molar ratio of 1: 1. A guanidine flame retardant mixed in a proportion of from 1.5 to 0.2 to 3 is added in an amount of 100 to 200% by weight based on the weight of the solid content of the synthetic resin, and the inorganic paper is then dried by heating to synthesize the synthetic resin. It is characterized in that the methylol group in the resin is crosslinked and the synthetic resin and the guanidine flame retardant are crosslinked.

According to the present invention described above, the methylol group in the synthetic resin contained in the inorganic paper is dehydrated and condensed during heating and drying to cause a crosslinking reaction, and the synthetic resin and the guanidine-based flame retardant are separated from each other. By causing a cross-linking reaction, in addition to the excellent flame retardancy inherent in inorganic paper,
It is possible to produce a flame-retardant paper that also has an even higher compression strength. When a paper honeycomb core is produced using the flame-retardant paper produced in this way, a paper honeycomb core excellent in flame retardancy and compressive strength can be obtained.

Fibers used in the inorganic paper of the present invention include bleached softwood kraft pulp (NBKP), bleached hardwood kraft pulp (LBKP), bleached softwood sulphite pulp (NBSP), bleached sulphite hardwood (LBSP) and sap. -Momechanical pulp (TMP), other wood pulp, and the like, and one or more of these can be appropriately selected and used. In addition to the above wood pulp, synthetic fibers such as polyester and nylon may be used together in an amount of less than 10% by weight based on the total fiber weight, whereby the dimensional stability of the inorganic paper can be improved. Further, if necessary, inorganic fibers such as glass fibers and rock wool may be used in combination with 5 to 15% by weight of the total fiber weight.
This can improve the compressive strength of the inorganic paper.

As the flame-retardant inorganic powder used for the inorganic paper, aluminum hydroxide, magnesium hydroxide and the like can be preferably used. Since these inorganic powders undergo endothermic decomposition when heated and release water of crystallization, they have self-extinguishing properties, and as a result, they can be used as particularly excellent flame-retardant inorganic powders.

Such a flame-retardant inorganic powder is added to the fiber at the stage of paper making in the range of 65 to 80% by weight based on the absolute dry weight,
Inorganic paper can be produced by paper making using a known method, for example, a cylinder paper machine, a Fourdrinier paper machine, a cylinder / Fourdrinier combination paper machine, an inclined short-strip paper machine, and the like. If it is attempted to contain the inorganic powder in an amount of more than 80% by weight, the yield becomes poor during papermaking. Even if the inorganic powder can be contained in a larger amount than 80% by weight, such an inorganic paper is excellent in flame retardancy but inferior in compressive strength. That is, JIS-P-812
It has been found that if the compressive strength according to 6 is 15 kgf or more, there is practically no problem for a paper honeycomb core, but an inorganic paper containing an inorganic powder in an amount of more than 80% by weight is used as a standard. Compressive strength is so low that it cannot reach Further, even if this criterion is satisfied, a higher compressive strength is preferable in terms of workability. On the other hand, when the content of the inorganic powder is less than 65% by weight, the resulting inorganic paper has a good compressive strength but is inferior in flame retardancy and cannot be applied as a flame retardant paper for paper honeycomb core.

The basis weight of the inorganic paper to be made into paper is 200 to 2
It is preferably 40 g / m ² . Rice basis weight is 200g
If it is less than / m ² , the compressive strength is relatively lowered when the honeycomb core is produced, and if it exceeds 240 g / m ² , the manufacturing cost becomes high, which is disadvantageous.

Examples of the synthetic resin having a methylol group used in the present invention include a methyl chloride compound of vinyl chloride / ethylene / vinyl acetate copolymer and a methylol compound of polyacrylamide, a melamine resin, a urea resin, Pheno
Examples thereof include methylol compounds such as resin and aminophenol resin. Of these, one kind or two or more kinds of synthetic resins are appropriately selected and used in consideration of the softening point of the synthetic resin and the like. For example, if the methylol compound of vinyl chloride / ethylene / vinyl acetate copolymer is contained alone in the inorganic paper, the synthetic resin may have a relatively low softening point and adhere to the after-dryer in the papermaking process to stain the cylinder. . In such a case, adhesion to the cylinder can be prevented by using a synthetic resin having a relatively high softening point such as a methylol compound such as melamine resin or phenol resin.

The content of the synthetic resin having a methylol group in the inorganic paper is in the range of 2 to 10% by weight based on the solid weight of the synthetic resin and the absolute dry weight of the inorganic paper. If the content is less than 2% by weight, the compressive strength of the inorganic paper cannot reach the desired level. On the other hand, if the content exceeds 10% by weight, the compressive strength will increase to some extent, but the amount of combustibles in the inorganic paper will increase, and the calorific value during combustion will increase, which is not suitable.

In the present invention, in addition to the above-mentioned synthetic resin having a methylol group, a guanidine flame retardant is further contained in the inorganic paper. The content of the guanidine flame retardant in the inorganic paper is 100 to 20 with respect to the solid content weight of the synthetic resin having a methylol group contained in the inorganic paper.
The range is 0% by weight. If it is less than 100% by weight, the effect of suppressing the temperature during combustion of the obtained flame-retardant paper is low. On the other hand, 200
When the content of the flame-retardant paper is large, exceeding 5% by weight, the obtained flame-retardant paper has a high compression strength and a good effect of suppressing the temperature at the time of combustion, but it is disadvantageous because the manufacturing cost increases.

As the guanidine flame retardant used in the present invention, sulfamic acid or phosphoric acid, cyanoguanidine and formaldehyde in a molar ratio of 1: 1 to 1.5:
An aqueous solution obtained by mixing at a ratio of 0.2 to 3 can be used.

Sulfamic acid and phosphoric acid in the guanidine flame retardant exhibit a flame retarding effect by dehydrating and carbonizing the pulp fibers contained in the inorganic paper, and cyanoguanidine releases nitrogen gas during combustion. Since the flame retardant effect is exhibited by decreasing the oxygen concentration, sulfamic acid or phosphoric acid has a property that the flame retardant effect is higher than that of cyanoguanidine. Therefore, when the molar ratio of cyanoguanidine in the flame retardant aqueous solution is less than 1, the flame retardancy does not decrease so much, but the compressive strength decreases, and conversely, when the molar ratio of cyanoguanidine exceeds 1.5. If it becomes higher, flame retardancy cannot be obtained, which is not suitable.
On the other hand, formaldehyde in the guanidine-based flame retardant reacts very easily with a compound having an imino group (= NH) such as cyanoguanidine at room temperature to form an amino-methylol compound, which makes cyanoguanidine water-soluble. The amino-methylol compound produced in the flame retardant is
Similar to the methylol group in the synthetic resin, it dehydrates and condenses during heat drying to cause a cross-linking reaction, which contributes to the improvement of the compression strength of the flame-retardant paper. When the molar ratio of cyanoguanidine is 1 to 1.5, the content of formaldehyde is 0.1.
When it is less than 2, the methylolation is insufficient and the compression strength cannot be obtained. In addition, if the content of formaldehyde is 3 or more in molar ratio, the improvement of the compression strength will reach a ceiling, and the free formaldehyde will be vaporized to generate a so-called "formalin odor", which significantly deteriorates the working environment and should be avoided. Should be. Furthermore, when formaldehyde is used in a large amount in excess of 2 times the cyanoguanidine molar ratio, the "formalin odor" is generated during heating and drying as described above. It is desirable to keep it to 2 times or less.

As a method for incorporating a synthetic resin having a methylol group and a guanidine-based flame retardant into an inorganic paper, a predetermined amount of a mixture of the synthetic resin and the flame retardant may be included in the paper making process of the inorganic paper, or the inorganic paper may be added. A mixture of a synthetic resin and a flame retardant may be added after paper making. Specifically, using an apparatus such as a size press coater, a roll coater, a blade coater, a bar coater, an air knife coater on machine or off machine. It can be contained in the inorganic paper. Alternatively, the inorganic paper may be impregnated with a bath containing an aqueous solution of a mixture of a synthetic resin and a flame retardant, and then squeezed with a squeezing machine to adjust the content to a predetermined value.

The inorganic paper containing the synthetic resin having a methylol group and the guanidine-based flame retardant as described above is then dried by a known drier to obtain the methylol group in the synthetic resin and further the guanidine-based flame retardant. Along with dehydration condensation of the generated methylol group and a crosslinking reaction,
The flame-retardant paper of the present invention can be produced by cross-linking a synthetic resin and a flame retardant. By this heat drying, the moisture content of the inorganic paper according to the JIS method is usually 4% by weight.
It should be as follows. When a methylol compound of various synthetic resins as described above is used, heat drying is performed at a surface temperature of the dryer of 90 to 240 ° C. When the heating temperature is lower than 90 ° C, the cross-linking reaction of the methylol group and the cross-linking reaction of the synthetic resin and the flame retardant may not be completed sufficiently. Further, if the heating temperature is higher than 240 ° C., the inorganic powder in the inorganic paper releases water of crystallization and undergoes endothermic decomposition, which may result in loss of flame retardancy of the inorganic paper, which is not preferable. While being heated and dried, the methylol group undergoes a crosslinking reaction and further the synthetic resin and the flame retardant undergo a crosslinking reaction, resulting in a significant improvement in the compressive strength of the inorganic paper. It is possible to impart excellent flame retardancy and compressive strength to the core.

[0019]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these. All% in the examples and comparative examples are% by weight.

Examples 1 and 2 Paper was made on a Fourdrinier paper machine using aluminum hydroxide as the inorganic powder and bleached softwood kraft pulp as the fiber. The aluminum hydroxide content was 78% and the rice basis weight was 220 g / m ^2.
Papermaking of the inorganic paper of. This inorganic paper is 297mm × 2
It was cut into a sheet having a size of 10 mm and used for the following experiment.

As the synthetic resin having a methylol group, a methyl chloride compound of vinyl chloride / ethylene / vinyl acetate copolymer (trade name “Sumikaflex 830”, manufactured by Sumitomo Chemical Co., Ltd.) 66%, a methylol compound of polyacrylamide (trade name “ Santax SP67 ", manufactured by Mitsui Toatsu) 17
%, 17% of a melamine resin methylol compound (trade name “Euramine P6300”, manufactured by Mitsui Toatsu) was prepared as a synthetic resin mixed aqueous solution (solid content concentration 20%). Furthermore, a mixture (trade name "P2151", manufactured by Sanwa Chemical Co., Ltd.) of phosphoric acid, cyanoguanidine, and formaldehyde mixed in a molar ratio of 1: 1.4: 0.2 to this aqueous solution was used as a guanidine-based flame retardant. 1 for the weight of synthetic resin solids
06% (Example 1) and 196% (Example 2) were mixed to prepare a synthetic resin / flame retardant mixed aqueous solution.

The inorganic paper obtained above was mixed with this synthetic resin /
After impregnating with the flame retardant mixed aqueous solution, the impregnation amount is adjusted with a roll type squeezing machine, and the solid content of the synthetic resin is 2.4% per absolute dry weight of the inorganic paper and the synthetic resin solid content is 106%. Inorganic paper containing a combustible agent (Example 1), and inorganic paper containing 2.4% by weight of solid content of the inorganic paper per dry weight of synthetic resin and 196% of synthetic resin solid content of the flame retardant (Example 2). ) Was manufactured. These inorganic papers were heated and dried for 20 seconds in a drum dryer having a mirror-finished surface at 120 ° C. to produce flame-retardant papers with a water content of 3%.

The compression strength of the flame-retardant paper thus obtained was measured according to the method for testing the compression strength of paperboard (ring crush method) described in JIS-P-8126. Furthermore, a 25 mm cell paper honeycomb core made by using these flame-retardant papers was subjected to a base material test by the method described in Ministry of Construction Notification No. 1828, and the heat generation temperature during combustion was 4
The pass / fail judgment was made by accepting one having a temperature of 0 ° C. or lower and rejecting one having a temperature higher than 40 ° C. The results are shown in Table 1.

Examples 3 and 4 In the same manner as in Example 1, except that inorganic paper containing 68% aluminum hydroxide was used as the inorganic powder.
A flame-retardant paper (Example 3) made of an inorganic paper containing 2.4% by weight of solid content of the inorganic resin per absolute dry weight of the synthetic resin and 106% of the synthetic resin by weight of the solid content of the synthetic resin, and the weight of the solid content. Thus, a flame-retardant paper (Example 4) made of an inorganic paper containing 2.4% of a synthetic resin based on the dry weight of the inorganic paper and 196% of a flame retardant based on the weight of the solid content of the synthetic resin was produced. Table 1 shows the results obtained by measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

Example 5 In the same manner as in Example 1 except that inorganic paper containing 78% aluminum hydroxide was used as the inorganic powder.
A flame-retardant paper made of an inorganic paper containing 9.6% by weight of solid content of the inorganic paper per absolute dry weight and 196% of the flame-retardant by weight of the synthetic resin solid content was produced. Table 1 shows the results of measuring the compressive strength of this flame-retardant paper and further conducting a substrate test on a paper honeycomb core made from this flame-retardant paper.

Comparative Examples 1 and 2 By the same method as in Example 1 except that an inorganic paper containing 82% aluminum hydroxide was used as the inorganic powder.
A flame-retardant paper (Comparative Example 1) made of an inorganic paper containing 2.4% by weight of solid content of the inorganic paper per absolute dry weight of the synthetic resin and 106% of the synthetic resin by weight of the solid content of the synthetic resin, and the weight of the solid content. Thus, a flame-retardant paper (Comparative Example 2) made of an inorganic paper containing 2.4% of a synthetic resin based on the absolute dry weight of the inorganic paper and 196% of a flame retardant based on the weight of the solid content of the synthetic resin was prepared. Table 1 shows the results obtained by measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

Comparative Examples 3 and 4 By the same method as in Example 1 except that inorganic paper containing 62% of aluminum hydroxide was used as the inorganic powder.
A flame-retardant paper (Comparative Example 3) made of an inorganic paper containing 2.4% by weight of solid content of inorganic paper per absolute dry weight of the synthetic resin and 106% of flame retardant per weight of the synthetic resin solid content, and solids weight. Thus, a flame-retardant paper (Comparative Example 4) made of an inorganic paper containing 2.4% of a synthetic resin based on the absolute dry weight of the inorganic paper and 196% of a flame retardant based on the solid content of the synthetic resin was prepared. Table 1 shows the results obtained by measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

Comparative Example 5 By the same method as in Example 1 except that inorganic paper containing 78% aluminum hydroxide was used as the inorganic powder.
A flame-retardant paper consisting of an inorganic paper containing 2.4% by weight of solid content of the inorganic paper per absolute dry weight of the synthetic resin and 96% of flame retardant based on the weight of the solid content of the synthetic resin was produced. Table 1 shows the results of measuring the compressive strength of this flame-retardant paper and further conducting a substrate test on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 6 By the same method as in Example 1 except that an inorganic paper containing 68% aluminum hydroxide was used as the inorganic powder.
A flame-retardant paper consisting of an inorganic paper containing 2.4% by weight of solid content of the inorganic paper per absolute dry weight of the synthetic resin and 96% of flame retardant based on the weight of the solid content of the synthetic resin was produced. Table 1 shows the results of measuring the compressive strength of this flame-retardant paper and further conducting a substrate test on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 7 By the same method as in Example 1 except that an inorganic paper containing 78% aluminum hydroxide was used as the inorganic powder.
A flame-retardant paper consisting of an inorganic paper containing 11.0% by weight of solid content of the inorganic paper per dry weight of the inorganic paper and 196% of flame retardant based on the weight of the solid content of the synthetic resin was produced. Table 1 shows the results of measuring the compressive strength of this flame-retardant paper and further conducting a substrate test on a paper honeycomb core made from this flame-retardant paper.

[0031]

[Table 1] Inorganic powder Synthetic resin Flame retardant Flame retardant paper Physical properties Content rate (%) Content rate (%) Content rate (%) Compressive strength (kgf) Substrate test Example 1 78 2.4 106 17 Pass Example 2 78 2.4 196 18 Pass Example 3 68 68 2.4 106 24 Pass Example 4 68 2.4 196 25 25 Pass Example 5 78 9.6 196 36 36 Pass Comparative Example 1 82 2.4 106 6 Pass Comparative example 2 82 2.4 196 12 Pass Comparative example 3 62 2.4 106 28 28 Fail Comparative example 4 62 2.4 196 29 29 Fail Comparative example 5 78 2.4 96 16 Fail Comparative example 6 68 2.4 96 23 Fail Comparative Example 7 78 11.0 196 40 Fail

Example 6 Using the same synthetic resin mixed aqueous solution as in Example 1, guanidine phosphate (trade name "Apinone 335", manufactured by Sanwa Chemical Co., Ltd., phosphoric acid and cyanoguanidine in a molar ratio of 1: 1) was used. A mixture with formaldehyde (genuine reagent, manufactured by Wako Pure Chemical Industries) (phosphoric acid: cyanoguanidine: formaldehyde was mixed at a molar ratio of 1: 1.0: 0.3) was added to the synthetic resin solid content weight. On the other hand, 138% was mixed to prepare a synthetic resin / flame retardant mixed aqueous solution having a solid content of 20%. The same inorganic paper having an aluminum hydroxide content of 78% as in Example 1 was impregnated with this synthetic resin / flame retardant mixed aqueous solution, and then the impregnation amount was adjusted with a roll type squeezing machine, and the inorganic paper was completely dried by solid content weight. A flame-retardant paper consisting of an inorganic paper containing 2.4% by weight of synthetic resin and 138% of flame-retardant per solid of the synthetic resin was produced. Table 2 shows the results of measuring the compressive strength of this flame-retardant paper and further conducting a substrate test on a paper honeycomb core made from this flame-retardant paper.

Example 7 Example 6 was repeated, except that the mixing ratio of phosphoric acid, cyanoguanidine and formaldehyde was phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.0: 2.0. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Example 8 Example 6 was repeated except that the mixing ratio of phosphoric acid, cyanoguanidine and formaldehyde was phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.4: 0.3 in molar ratio. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Example 9 Example 6 was repeated except that phosphoric acid, cyanoguanidine and formaldehyde were added at a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.4: 2.0. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 8 Example 6 was repeated except that phosphoric acid, cyanoguanidine and formaldehyde were added in a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 0.9: 0.3. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 9 Comparative Example 9 was repeated except that phosphoric acid, cyanoguanidine and formaldehyde were added in a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 0.9: 2.0. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 10 Example 6 was repeated, except that phosphoric acid, cyanoguanidine and formaldehyde were added in a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.6: 0.2. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 11 As Example 6 except that phosphoric acid, cyanoguanidine and formaldehyde were added in a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.6: 2.0. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the inorganic paper, and 115% by weight of the synthetic resin solid content of the flame retardant was produced. Table 2 shows the results of measuring the compressive strength of this flame-retardant paper and further conducting a substrate test on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 12 As Example 6 except that phosphoric acid, cyanoguanidine and formaldehyde were added at a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.0: 0.1. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 13 Example 6 was repeated except that phosphoric acid, cyanoguanidine and formaldehyde were added at a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.4: 0.1. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 14 As Example 6 except that phosphoric acid, cyanoguanidine and formaldehyde were added at a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.0: 2.5. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

Comparative Example 15 Example 6 was repeated except that phosphoric acid, cyanoguanidine and formaldehyde were added at a molar ratio of phosphoric acid: cyanoguanidine: formaldehyde = 1: 1.4: 2.5. In the same manner, a flame-retardant paper made of an inorganic paper containing 2.4% by weight of solid content of the synthetic resin and 115% of the flame retardant per solid content of the synthetic resin was produced. Measure the compressive strength of this flame-retardant paper,
Table 2 shows the results of a base material test performed on a paper honeycomb core made from this flame-retardant paper.

[0044]

[Table 2] Mixing ratio of flame retardant (molar ratio) Phosphoric acid: Cyanoguanidine flame retardant paper Physical properties : Formaldehyde compressive strength (kgf) Substrate test Example 6 1: 1.0: 0.3 15 15 Pass Example 7 1 : 1.0: 2.0 16 Pass Example 8 1: 1.4: 0.3 16 Pass Example 9 1: 1.4: 2.0 20 Pass Comparative Example 8 1: 0.9: 0.3 11 Passed Comparative Example 9 1: 0.9: 2.0 14 Passed Comparative Example 10 1: 1.6: 0.2 18 Failed Comparative Example 11 1: 1.6: 2.0 21 Failed Failed Comparative Example 12 1 : 1.0: 0.1 12 Passed Comparative Example 13 1: 1.4: 0.1 12 Passed Comparative Example 14 1: 1.0: 2.5 18 18 Passed Comparative Example 15 1: 1.4: 2.5 20 pass

As can be seen from Tables 1 and 2, the flame-retardant paper of the present invention has a compressive strength of 15 kgf or more and is excellent in flame retardancy (Examples 1 to 9). The compressive strength is affected by the content of the inorganic powder in the inorganic paper and the mixing ratio of cyanoguanidine or formaldehyde in the guanidine flame retardant. The upper limit of the content of the inorganic powder to the compressive strength is 8
The flame-retardant paper having a content of 0% and an inorganic powder content higher than 0% has extremely low compression strength and excellent flame retardancy, but is not suitable for practical use (Comparative Examples 1 and 2). On the other hand, if the content of the inorganic powder is less than 65%, the compressive strength is excellent, but the flame retardance is poor, and therefore it is not suitable for practical use (Comparative Examples 3 and 4).

Even if the content of the inorganic powder is within the proper range, even if the content of the guanidine-based flame retardant per solid content of the synthetic resin having a methylol group is low, the compression is performed. Although it has high strength, it is inferior in flame retardance and thus not suitable for practical use (Comparative Examples 5 to 6). Further, even if the content of the synthetic resin is too high, the flame retardance is poor and it is not suitable for practical use (Comparative Example 7).

Even if the flame retardant paper has the content of the inorganic powder, the content of the synthetic resin, and the content of the guanidine-based flame retardant based on the solid content of the synthetic resin within the proper range, the flame retardant is constituted. When the mixture ratio of phosphoric acid: cyanoguanidine: formaldehyde is low in cyanoguanidine (Comparative Examples 8 to 9) or low in formaldehyde (Comparative Examples 12 to 13), flame retardancy is obtained in both cases. Excellent but poor compressive strength. Furthermore, when the mixing ratio by the molar ratio of cyanoguanidine in the guanidine-based flame retardant is high (when the mixing ratio of phosphoric acid is relatively low), the flame retardance is inferior (Comparative Examples 10 to 1).
1). The upper limit of the mixing ratio of formaldehyde in the guanidine-based flame retardant is twice the molar ratio of cyanoguanidine, but if the ratio of formaldehyde is higher than this, the flame retardancy and compressive strength are excellent, but the mixing ratio is high. No improvement in compressive strength commensurate with the proportion was observed, and rather free formaldehyde was vaporized in the heating and drying process, causing a severe irritating odor and unsuitable for practical use in environmental hygiene (Comparative Examples 14 to 15). .

[0048]

As described above, the flame-retardant paper according to the present invention comprises a flame-retardant inorganic paper containing a synthetic resin having a methylol group and a guanidine-based flame retardant, and heat-drying the methylol to make the methylol. It has a high compressive strength and excellent flame retardancy because it is a product of crosslinking reaction between a group and a synthetic resin and a flame retardant. As a result, the paper honeycomb core made from this flame-retardant paper has excellent flame retardancy and compressive strength, and is also widely used as a paper honeycomb core for building base materials that require these physical properties. can do.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichiro Uematsu 1-10-6 Shinonome, Koto-ku, Tokyo Shin-Oji Paper Co., Ltd. Tokyo Product Laboratory (72) Inventor Yasuyuki Yamaji 8-10 Shimorenjaku, Mitaka City, Tokyo No. 16 Nittetsu Mining Co., Ltd. (72) Inventor Satoshi Nakamura No. 16-16 Shimorenjaku, Mitaka-shi, Tokyo Inside Nittetsu Mining Co., Ltd.

Claims (1)

[Claims] 1. An inorganic paper, which comprises paper and a flame-retardant inorganic powder as main components and contains said inorganic powder in an amount of 65 to 80% by weight based on an absolute dry weight, having (1) a methylol group. 2 to 10% by weight of the synthetic resin in terms of solid content based on the absolute dry weight of the inorganic paper, and (2) sulfamic acid or phosphoric acid, cyanoguanidine and formaldehyde in a molar ratio of 1: 1 to 1.5: 0.2
A guanidine-based flame retardant mixed at a ratio of 3 is contained in an amount of 100 to 200% by weight based on the solid content of the synthetic resin, and then the inorganic paper is dried by heating to crosslink the methylol group in the synthetic resin. A method for producing a flame-retardant paper for a paper honeycomb core, characterized in that the synthetic resin and the guanidine-based flame retardant are cross-linked with each other.