Flame retardant paper and preparation method thereof

Abstract

The invention discloses a flame-retardant paper, which is prepared from pulp after pulping, a phosphorus-nitrogen flame retardant, a cationic agent, and a retention and drainage aid system through an in-pulp addition method. The raw materials are mixed evenly, formed into sheets, pressed, and dried to obtain the flame-retardant paper. The cationic agent can effectively neutralize the negative charge of the phosphorus-nitrogen flame retardant, alleviate the hydrolysis of the phosphorus-nitrogen flame retardant, and synergistically improve the flame retardant effect of the paper. At the same time, the sizing agent can make the paper have a certain water resistance, improve the printing performance of the paper, improve the durability and strength of the paper, prevent the flame retardant in the paper from hydrolyzing in a humid environment, and avoid the problem of reduced mechanical strength and weakened flame retardant effect of the paper.

Description

Technical Field

[0001] The invention relates to flame retardant paper and a preparation method thereof, belonging to the field of special paper manufacturing. Background Art

[0002] Cellulose paper is mostly made of plant fibers, which have the advantages of natural biodegradability, recyclability, light weight and low cost, and are widely used in culture, packaging, home decoration, textile and other fields. However, it also has disadvantages such as flammability and susceptibility to moisture, which to some extent affect its basic performance and application range.

[0003] Phosphorus-nitrogen flame retardant is an important halogen-free gas and acid source flame retardant, mainly including: ammonium polyphosphate (APP), melamine polyphosphate (PNA), ammonium phosphate salt, etc. As a highly efficient intumescent flame retardant system, phosphorus-nitrogen flame retardant has the advantages of high phosphorus-nitrogen content, good thermal stability, tight carbon layer, low smoke emission, etc. It is widely used in flame retardant modification of polymers, coatings, wood products and various fiber materials. However, phosphorus-nitrogen flame retardants have strong hygroscopicity and are easily hydrolyzed and migrated in a humid environment, which reduces their flame retardant properties. During the addition process in the pulp, the phosphorus-nitrogen flame retardant is hydrolyzed, and the ammonium radical (NH4 + ) is partially ionized and exhibits strong negative charge in water, which has a great influence on the retention of flame retardant in the slurry. That is, the flame retardant is easily lost with water during the addition process in the slurry, and the flame retardant effect is not ideal.

[0004] At present, the preparation of flame-retardant paper usually adopts the dipping method or coating method. These methods increase the production operation links and cannot achieve the intrinsic flame retardancy and hydrophobicity of paper. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a flame retardant paper and a preparation method thereof which can improve the retention of flame retardants through the synergistic effect of a cationic agent and a phosphorus-nitrogen flame retardant.

[0006] In order to solve the above technical problems, the present invention firstly discloses a flame retardant paper, which is prepared by pulping treated pulp, phosphorus nitrogen flame retardant, cationic agent and retention and drainage system through an in-pulp adding method.

[0007] Furthermore, the raw materials for preparing the flame retardant paper also include a sizing agent.

[0008] Furthermore, the sizing agent is one of alkyl ketene dimer (AKD), cationic rosin or anionic rosin; the addition amount of alkyl ketene dimer is 0.05wt%-0.5wt% of the absolute dry fiber of pulp, and the addition amount of cationic rosin or anionic rosin is 0.5wt%-5.0wt% of the absolute dry fiber of pulp.

[0009] Furthermore, the phosphorus-nitrogen flame retardant is one of ammonium polyphosphate (APP), melamine polyphosphate (MPP), melamine modified ammonium polyphosphate (MFAPP) or ammonium phosphate, and the added amount is 15wt%-65wt% of the absolute dry fiber of pulp.

[0010] Furthermore, the cationic agent is an organic polymer with low molecular weight and high cationic charge density, specifically one or more of polydiallyldimethylammonium chloride (PDDA), polyethyleneimine (PEI), polyamide epichlorohydrin (PAE) or polyamine (polyEPI-DA), and the added amount is 0.5wt%-5.0wt% of the absolute dry fiber of pulp.

[0011] Furthermore, the retention and drainage aid system is cationic polyacrylamide (CPAM), and the addition amount is 0.02wt%-0.1wt% of the absolute dry fiber of the pulp.

[0012] Furthermore, the retention and drainage aid system is cationic polyacrylamide (CPAM) and bentonite particles, the amount of cationic polyacrylamide (CPAM) added is 0.02wt%-0.1wt% of the absolute dry fiber of the pulp, and the amount of bentonite particles added is 0.1wt%-0.4wt% of the absolute dry fiber of the pulp. The retention and drainage aid system obtained by combining with bentonite particles has a better retention effect on the flame retardant than when cationic polyacrylamide is used alone.

[0013] The present invention also discloses a method for preparing the flame retardant paper. After pulping, phosphorus-nitrogen flame retardant, cationic agent and retention and drainage system are sequentially added while stirring, mixed evenly, formed into sheets, pressed and dried to obtain hydrophobic flame retardant paper.

[0014] Furthermore, when the raw materials contain a sizing agent, the process may be as follows: after pulp beating, the sizing agent, phosphorus-nitrogen flame retardant, cationic agent, and retention and drainage aid system are sequentially added while stirring, mixed evenly, sheeted into shape, pressed, and dried to obtain hydrophobic flame-retardant paper.

[0015] Furthermore, when the raw materials contain a sizing agent, the process can be as follows: after pulp beating, phosphorus-nitrogen flame retardant, sizing agent, cationic agent, retention and drainage aid system are added in sequence while stirring, mixed evenly, formed into sheets, pressed, and dried to obtain hydrophobic flame retardant paper.

[0016] The pulp is unbleached softwood kraft pulp or other types of pulp, such as unbleached hardwood kraft pulp, bleached softwood kraft pulp, bleached hardwood kraft pulp, etc., and the pulp beating degree is 15-65°SR.

[0017] Cationic agent is an organic polymer with low molecular weight and high positive charge density. It has strong positive charge and can effectively neutralize the negative charge of phosphorus nitrogen flame retardant, alleviate the hydrolysis of phosphorus nitrogen flame retardant, and synergistically improve the flame retardant effect of paper. At the same time, the sizing agent can make the paper have a certain water resistance, improve the printing performance of paper, improve the durability and strength of paper, prevent the hydrolysis of flame retardant in paper in a humid environment, and avoid the problem of reduced mechanical strength and weakened flame retardant effect of paper. The retention and filtration system can further improve the retention rate of phosphorus nitrogen flame retardant in the pulp, which can not only make the paper realize intrinsic flame retardancy and improve flame retardant performance, but also can improve the hydrophobicity of paper in combination with the sizing agent, and can also reduce production costs, and is easy to industrialize and mass produce. In the process of adding in the pulp of the present invention, the sizing agent can be added first and then the phosphorus nitrogen flame retardant, or the phosphorus nitrogen flame retardant can be added first and then the sizing agent. The sizing agent is added first and then the phosphorus-nitrogen flame retardant is added, which effectively improves the hydrophobicity of the flame-retardant paper and increases the Cobb value of the paper by 36% compared with the paper to which the phosphorus-nitrogen flame retardant is added first. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a line graph showing the effect of the amount of ammonium polyphosphate (APP) added on the flame retardant properties of paper and the LOI value of paper under the coordination of different cationic agents;

[0019] Figure 2 It is a line graph showing the effect of the amount of cationic agent polydiallyl dimethyl ammonium chloride (PDDA) added on the flame retardant properties of paper and the LOI value of paper;

[0020] Figure 3 This is a line graph showing the effect of the amount of sizing agent alkyl ketene dimer (AKD) added on the surface water absorption of paper and paperboard and the Cobb value of paper. DETAILED DESCRIPTION

[0021] The present invention is further explained below in conjunction with the examples. The following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0022] 1. The following Examples 1 to 3 illustrate the effect of the amount of phosphorus-nitrogen flame retardant added on the flame retardant properties of paper under the synergistic effect of a cationic agent.

[0023] Example 1

[0024] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 25% APP suspension, 5% PDDA, 0.1% CPAM, and 0.2% bentonite particles (all amounts are percentages by mass relative to absolute dry fiber of the pulp) are added to the pulp in sequence, mixed evenly, sheeted into shape, pressed, and dried to obtain flame-retardant paper.

[0025] Through testing, the flame-retardant paper prepared in Example 1 has a LOI value of 36.8% when 25% APP and 5% PDDA act synergistically.

[0026] Example 2

[0027] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 30% APP suspension, 5% PDDA, 0.1% CPAM, and 0.2% bentonite particles (all amounts are percentages by mass relative to absolute dry fiber of the pulp) are added to the pulp in sequence, mixed evenly, sheeted into shape, pressed, and dried to obtain flame-retardant paper.

[0028] Through testing, the flame-retardant paper prepared in Example 2 has a LOI value of 45.6% when 30% APP and 5% PDDA act synergistically.

[0029] Example 3

[0030] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 35% APP suspension, 5% PDDA, 0.1% CPAM, and 0.2% bentonite particles (all amounts are percentages by mass relative to absolute dry fiber of the pulp) are added to the pulp in sequence, mixed evenly, sheeted into shape, pressed, and dried to obtain flame-retardant paper.

[0031] Through testing, the flame-retardant paper prepared in Example 3 has a LOI value of 50.7% when 35% APP and 5% PDDA act synergistically.

[0032] Conclusion 1: Based on Examples 1 to 3, and Figure 1 It was concluded that under the synergistic effect of the cationic agent and the phosphorus-nitrogen flame retardant, the flame-retardant paper prepared in pulp had good flame retardant properties. When the amount of cationic agent was constant, the flame retardant properties improved with the increase of the amount of phosphorus-nitrogen flame retardant.

[0033] In addition, research has found that: under the coordination of cationic agents, flame retardant dosage in the range of 15-65% has good flame retardant effect. Within this range, the higher the amount of flame retardant added, the better the flame retardant effect. From an economic point of view, when the addition amount is between 20% and 40%, it can ensure that the flame retardant paper has excellent flame retardant effect while also having good economic cost recovery. Therefore, the best application range of flame retardant is 20%-40%.

[0034] 2. The following Examples 4 to 5 illustrate the effect of the order of adding the sizing agent and the phosphorus-nitrogen flame retardant on the flame retardancy and hydrophobicity of paper.

[0035] Example 4

[0036] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 0.3% AKD, 30% APP suspension, 3% PDDA, 0.1% CPAM, and 0.2% bentonite particles are added to the pulp in sequence (all amounts are percentages by mass relative to the absolute dry fiber of the pulp), mixed evenly, sheeted into shape, pressed, and dried to obtain hydrophobic flame retardant paper.

[0037] Through testing, the Cobb value of the hydrophobic flame-retardant paper prepared in Example 4 is 35 g / m 2 , the LOI value is 40.2%.

[0038] Example 5

[0039] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 30% APP suspension, 0.3% AKD, 3% PDDA, 0.1% CPAM, and 0.2% bentonite particles (all amounts are percentages by mass relative to absolute dry fiber of the pulp) are added to the pulp in sequence, mixed evenly, sheeted into shape, pressed, and dried to obtain hydrophobic flame-retardant paper.

[0040] Through testing, the Cobb value of the hydrophobic flame-retardant paper prepared in Example 5 is 55g / m 2 , the LOI value is 39.2%.

[0041] Conclusion 2: Based on Examples 4 and 5, adding the sizing agent first can achieve better flame retardant and hydrophobic effects than adding the flame retardant first. Compared with Example 5, the Cobb value of the paper in Example 4 is increased by 36%.

[0042] 3. The following Examples 6 to 9 illustrate the effect of the amount of cationic agent on the flame retardancy and hydrophobicity of paper.

[0043] Example 6

[0044] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 0.3% AKD, 30% APP suspension, 0.1% CPAM, and 0.2% bentonite particles are added to the pulp in sequence (all amounts are percentages by mass relative to the absolute dry fiber of the pulp), mixed evenly, sheeted into shape, pressed, and dried to obtain hydrophobic flame-retardant paper.

[0045] Through testing, the Cobb value of the hydrophobic flame-retardant paper prepared in Example 6 is 42 g / m 2 , the LOI value is 32.2%.

[0046] Example 7

[0047] Beat natural softwood kraft pulp or other types of pulp to 32°SR, weigh the pulp according to the quantitative amount of 200g / m2 paper, add 0.3% AKD, 30% APP suspension, 0.5% PDDA, 0.1% CPAM, and 0.2% bentonite particles (all amounts are percentages by mass relative to the absolute dry fiber of the pulp) into the pulp in sequence, mix well, sheet-form into shape, press, and dry to obtain hydrophobic flame-retardant paper.

[0048] Through testing, the Cobb value of the hydrophobic flame-retardant paper prepared in Example 7 is 40 g / m 2 , the LOI value is 33.6%.

[0049] Example 8

[0050] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 0.3% AKD, 30% APP suspension, 3% PDDA, 0.1% CPAM, and 0.2% bentonite particles are added to the pulp in sequence (all amounts are percentages by mass relative to the absolute dry fiber of the pulp), mixed evenly, sheeted into shape, pressed, and dried to obtain hydrophobic flame retardant paper.

[0051] Through testing, the Cobb value of the hydrophobic flame-retardant paper prepared in Example 8 is 35 g / m 2 , the LOI value is 40.2%.

[0052] Example 9

[0053] Beat the natural softwood kraft pulp or other types of pulp to 32°SR, according to 200g / m 2 Paper pulp is quantitatively weighed, and 0.3% AKD, 30% APP suspension, 5% PDDA, 0.1% CPAM, and 0.2% bentonite particles are added to the pulp in sequence (all amounts are percentages by mass relative to the absolute dry fiber of the pulp), mixed evenly, sheeted into shape, pressed, and dried to obtain hydrophobic flame retardant paper.

[0054] Through testing, the Cobb value of the hydrophobic flame-retardant paper prepared in Example 9 is 32 g / m 2 The LOI value is 43.9%, reaching the flame retardant level and having good hydrophobic properties.

[0055] Conclusion 3: Based on Examples 6 to 9, the cationic agent and the flame retardant have a good synergistic flame retardant effect. The experiment found that as the amount of cationic agent increases, the synergistic effect increases, but when the amount is too high, the pulp is in a highly flocculated state. Although the LOI value is still slightly increased, it will affect other properties, such as the uniformity and tensile strength of the paper.

Claims

1. A method for preparing flame retardant paper, characterized in that: After the pulp is beaten, a sizing agent, a phosphorus-nitrogen flame retardant, a cationic agent, and a retention and drainage aid system are added in sequence while stirring, mixed evenly, formed into a sheet, pressed, and dried to obtain a hydrophobic flame retardant paper; The phosphorus-nitrogen flame retardant is added in an amount of 15wt%-65wt% of the absolute dry fiber of the pulp; The cationic agent is one or more of polydiallyldimethylammonium chloride, polyethyleneimine, polyamide epichlorohydrin or polyamine, and the added amount is 0.5wt%-5.0wt% of the absolute dry fiber of pulp.

2. The method for preparing the flame retardant paper according to claim 1, characterized in that: The sizing agent is one of alkyl ketene dimer, cationic rosin or anionic rosin; the addition amount of the alkyl ketene dimer is 0.05wt%-0.5wt% of the absolute dry fiber of pulp, and the addition amount of the cationic rosin or anionic rosin is 0.5wt%-5.0wt% of the absolute dry fiber of pulp.

3. The method for preparing the flame retardant paper according to claim 1, characterized in that: The phosphorus-nitrogen flame retardant is one or more of ammonium polyphosphate, melamine polyphosphate, melamine-modified ammonium polyphosphate or ammonium phosphate salt.

4. The method for preparing the flame retardant paper according to claim 1, characterized in that: The retention and drainage aid system is cationic polyacrylamide, and the addition amount is 0.02wt%-0.1wt% of the absolute dry fiber of the pulp.

5. The method for preparing the flame retardant paper according to claim 1, characterized in that: The retention and drainage aid system is cationic polyacrylamide and bentonite particles, wherein the amount of cationic polyacrylamide added is 0.02wt%-0.1wt% of the absolute dry fiber of the pulp, and the amount of bentonite particles added is 0.1wt%-0.4wt% of the absolute dry fiber of the pulp.

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