JPH06257098A - Softening agent of paper - Google Patents

Abstract

PURPOSE:To obtain a softening agent for paper excellent in softening effect of paper and paper strength and free from occurrence of paper powder. CONSTITUTION:The softening agent of paper consists essentially of a water-soluble heat reacting type urethane resin obtained by blocking an isocyanate group of a urethane prepolymer consisting of a silicone polyol or the silicone polyol and a polyether polyol and an organic polyisocyanate and having >=2 isocyanate groups in the molecule and having 1.0-6.0wt.% terminal isocyanate groups with a blocking agent capable of regenerating the isocyanate group by heat treatment.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a paper softener.

[0002]

As a conventional softening agent and softening method for paper, for example, in terms of chemicals, an aqueous softening agent such as polyethylene wax type emulsion and silicone oil emulsion generally used for fiber clothing is used. There is a method of softening. On the other hand, in terms of processing, tissue paper, toilet paper, towel paper,
Crepe processing that is carried out with kitchen wiper paper,
The feeling of touch has been made flexible by processing such as embossing.
Flexible processing can be mentioned. In addition, the conventional water-based softening agent and the combined softening processing such as the crepe processing and the embossing processing may be mentioned. More recently, attempts have been made to improve softness by selecting and combining types of virgin pulp found in tissue paper and the like.

[0003]

However, although polyethylene wax emulsions and silicone oil emulsions, which are conventional aqueous softeners, are effective in softening paper, they are attached to paper. As a result, the friction coefficient between the cellulose fibers decreases,
It has drawbacks such as a paper strength in a dry state and a wet state, and a paper strength such as a bending strength. Therefore, it becomes necessary to limit the adhesion amount within a low range, and as a result, the above-mentioned conventional aqueous softening agents have not yet achieved the improved softening processing of paper.

On the other hand, the creping process, embossing process and the like which are carried out on the above-mentioned tissue paper, toilet paper, towel paper, kitchen wiper paper, etc.
Although the softening effect is repelled by the change in the surface shape of the paper, even in this case, the kind of the target paper is limited and it cannot be applied to all kinds.

In the crepe process, when the above-mentioned conventional water-based softening agent is adhered and executed, the paper tends to be peeled from the drum dryer surface due to the releasing effect of these softening agents, so that a good denseness is obtained. It has been pointed out that a simple crepe process cannot be achieved.

On the other hand, in improving the softening by selecting / combining the types of virgin pulp which has been recently studied, there is a problem such as an increase in price, and it is necessary to limit the use purpose. There is.

Further, Japanese Patent Application No. 3-225245 discloses a heat-reactive urethane resin as a paper strengthening agent.
This heat-reactive urethane resin has an excellent effect of increasing paper strength, but has a problem that it is not sufficient for softening paper.

[0008] The utilization of waste paper is one of the things that has been actively studied as a recent resource saving measure. In the used paper, applications requiring the above-mentioned softening, for example, it has been attempted to be used for toilet paper and the like, but the used paper has a short fiber length and weak entanglement between celluloses, compared with paper made of new pulp. Paper strength is extremely weak. When such a used paper is coated with the above-mentioned conventional water-based softener,
At present, there are almost no application examples because the strength becomes unusable for practical use. Further, since waste paper has a short fiber length, there is a problem that when processed paper is used, for example, when the skin or the like is wiped, a large amount of paper dust is generated, and this is also expected to be improved.

As described above, the present invention is a softening agent for paper including waste paper, which is excellent in softening effect and paper strength, generates almost no paper dust, and when used in combination with creping, has a releasing action. The purpose of the present invention is to provide a softening agent that does not make the crepe process difficult to perform.

[0010]

The present invention has been made in view of such conventional problems, and it has been found that the above problems can be overcome by using a specific urethane resin as a softening agent. That is, a urethane having two or more isocyanate groups in a molecule composed of a silicone polyol compound or a silicone polyol compound and a polyether polyol, and an organic polyisocyanate, and having a terminal isocyanate of 1.0 to 6.0% by weight. It is a paper softening agent containing as an essential component a water-soluble heat-reactive urethane resin obtained by blocking an isocyanate group of a prepolymer with a blocking agent that regenerates the isocyanate group by heat treatment.

(Requirements Constituting Means) Main items relating to the configuration of the present invention will be described below. The water-soluble heat-reactive urethane resin used in the present invention basically comprises the following three components A), B), and C), and if necessary, the following D) and E) components are used. A) Silicone polyol compound, or silicone polyol compound and polyether polyol, B) Organic polyisocyanate compound, C) Blocking agent, D) Compound having ionic salt forming group and corresponding salt forming agent, E) Nonionic property Compound with hydrophilic group

Examples of the compound used in A) include a silicone polyol compound having an average molecular weight of 800 to 8000 and having two or more hydroxyl groups in the molecule, or a combination thereof with a polyether polyol.

Examples of the silicone polyol compound include the following compounds having a constitutional unit of organosiloxane and having at least two or more hydroxyl groups in the terminal and side chains in the molecule. That is,
It is composed of a unit and the following chemical unit 2 or the chemical formula 3 unit below.

[0014]

[Chemical 1]

[0015]

[Chemical 2]

[0016]

[Chemical 3] (In the above units, R _{1 to} R ₄ represent a methyl group or a phenyl group, R ₅ represents an oxyalkylene group, a polyoxyalkylene group or an alkylene group, and X represents a hydroxyl group.)

The polyether polyol used in combination with the silicone polyol compound as the component A) of the present invention is, for example, ethylene oxide, propylene oxide,
Homogeneous or copolymerized or polyadded polyether polyols such as butylene oxide, ethylene glycol,
Examples thereof include glycols such as diethylene glycol, butanediol, propylene glycol and hexanediol, triols such as trimethylolpropane and pentaerythritol, and polyether polyols obtained by polyadding the above alkylene oxide to tetraols. The mixing ratio of this polyether polyol is preferably 0 to 70% by weight based on the silicone polyol.

Examples of the compound used in the above B) include organic polyisocyanate compounds having two or more isocyanate groups in the molecule. For example, for example, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, isophorone diisocyanate,
Hexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, water-added toluene diisocyanate, tetramethylxylylene diisocyanate, and all aromatic, aliphatic, and alicyclic compounds conventionally used such as burette compounds and isocyanate compounds of these isocyanates. The isocyanates may be used alone or as a mixture.

Examples of the compound used in C) include a blocking agent which itself and an isocyanate adduct regenerate the isocyanate group by heat treatment. For example, phenol-substituted phenols such as phenol, butylphenol, nonylphenol, chlorophenol, and phenylphenol, oximes such as butanone oxime, cyclohexanone oxime, and acetoxime, imidazole, 2-methylimidazole, 2-ethylimidazole. Imidazoles such as
Examples thereof include substituted imidazoles, lactams such as ε-caprolactam, and acidic sulfite salts such as acidic sodium sulfite and acidic potassium sulfite.

Examples of the compound used in the above D) include a compound having a hydroxyl group and / or an amino group and an ionic salt forming group in the molecule, and a salt forming agent corresponding thereto. For example, as a compound having a salt-forming carboxylic acid or sulfonic acid group, for example, glycolic acid, malic acid, glycine aminobenzoic acid, hydroxyl acid such as dimethylolpropionic acid, aminocarboxylic acid, polycarboxylic acid Valent hydroxyl acid and taurine sulfamic acid,
Examples thereof include aminosulfonic acid such as 2-hydroxyethanesulfonic acid, hydroxysulfonic acid and the like.

Examples of salt forming agents corresponding thereto include monovalent metal hydroxides such as sodium hydroxide and potassium hydroxide, and amine compounds such as ammonia, trimethylamine and triethylamine. Examples of the compound having a group capable of becoming a quaternary or tertiary group that can be neutralized with an acid include N, N-dimethylethanolamine and N.
Examples thereof include alkoxylated amines such as -methyldiethanolamine, amino alcohols and amines such as N-methyl-N- (3-aminopropyl) -ethanolamine and N, N-dimethylhydrazine. Examples of salt-forming agents corresponding to these include organic and inorganic acids such as hydrochloric acid, nitric acid, formic acid, acetic acid, diethyl sulfuric acid, methyl chloride, benzyl chloride, xylylene dichloride, and halogens capable of quaternization reaction. Compounds containing atoms or esters of strong acids are mentioned.

Examples of the compound used in the above E) include compounds having a hydroxyl group and / or an amino group and a nonionic hydrophilic group in the molecule. For example,
Examples thereof include ethylene oxide homopolymers or mono- or polyhydric alcohols of ethylene oxide and propylene oxide addition polymers.

The component (A) used in the present invention and an organic polyisocyanate have two or more isocyanate groups in the molecule, and the terminal isocyanate group is 1.0 to
The composition of the urethane prepolymer having 6.0% by weight is
The components A), B) and C), or A), B),
The compound obtained by adding D) and / or E) to C) is carried out by a known method in the presence or absence of an organic solvent.

In the urethane prepolymer having an isocyanate group used here, when the final product of the present invention is processed into paper when the free isocyanate group at the terminal is less than 1.0% by weight, flexibility is exhibited. However, the effect of improving the paper strength is weak, and on the other hand, if it exceeds 6.0% by weight, it is effective for the effect of improving the paper strength, but the effect of achieving softening of the paper is weak, which is not preferable. Preferably 1.5 to 5.0% by weight
Is.

The blocked urethane prepolymer obtained above is diluted with water to form a final resin-processing liquid of the water-soluble heat-reactive urethane resin used in the present invention. The concentration of the resin-processing liquid is There is no particular limitation, as long as the paper has a predetermined amount of adhesion.

The softening method for paper is carried out by attaching a resin containing the water-soluble heat-reactive urethane resin as an essential component to the paper and heat-treating it. As a method for adhering the resin containing the water-soluble heat-reactive urethane resin as an essential component, either a method of impregnating paper with these resin processing liquids and squeezing, a method of spray coating these resin processing liquids on the paper, or the like is adopted. To be done. In the spray coating, spray coating can be performed after the paper making process.
From the viewpoint of efficiency, it is preferable to perform spray application on a blanket after the paper making step of the paper or spray application before the dryer drying in the subsequent step.

The amount of the softening agent of the present invention deposited is 0.03 to 0.50% by weight, more preferably 0.04 to 0.16% by weight, based on the pulp. When it is less than 0.03%, the improvement of paper strength is weakened, and when it exceeds 0.5%, elasticity is exhibited and flexibility is impaired.

Further, in the case of using in combination with crepe processing which is generally carried out for tissue, spray coating is applied before crepe processing, heat treatment is carried out to perform crepe processing, and spray coating is applied to creped paper. Any heat treatment method can be adopted.

The heat treatment condition is 100 to 180 ° C. By this heat treatment, the blocking agent dissociates, the free isocyanate group is regenerated, and the polymerization reaction starts.

The target papers are new pulp, waste paper pulp,
It can be applied to new / waste paper mixed pulp, and also mixed paper of natural pulp and synthetic fiber.

Further, the conventional aqueous softening agents described above may be used in combination for achieving further softening. However, it is necessary to set the amount of the conventional water-based softening agent used in combination in consideration of reduction in paper strength, but preferably, the water-soluble heat-reactive urethane resin used in the present invention: conventional water-based softening agent = 100 ~
A mixing ratio range of 70: 0 to 30 is preferable.

Further, as a combination aqueous softening agent which is more effective than the conventional aqueous softening agents such as polyethylene wax type emulsion and silicone oil emulsion, urethane type softening agent can be mentioned. The urethane softener referred to here is propylene oxide: ethylene oxide = 20.
It is preferable to use a non-reactive water-based urethane softening agent which is formed by reacting a polyether polyol copolymerized at a ratio of -50: 80 to 50% by weight with the organic polyisocyanate and has no terminal isocyanate.

[0033]

The water-soluble heat-reactive urethane resin used in the present invention uses a silicone polyol compound as a polyol component and, because of its molecular weight in the oligomer range, penetrates well into the cellulose fiber of paper, and is further heat-treated to give isocyanate. The paper strength is improved by recycling and polymerizing, and the paper is given a unique texture and softened. Further, since the cellulose fibers of the paper are bound to each other, almost no paper dust is generated.

Further, good crepe processing can be carried out without the release effect of the paper on the surface of the dryer found in conventional water-based softeners during crepe processing. Therefore, further softening can be achieved by softening the paper with the water-soluble heat-reactive urethane resin used in the present invention and softening the paper by favorable crepe surface treatment.

[0035]

EXAMPLES The present invention will now be described with reference to specific examples. The parts and% in the description mean parts by weight and% by weight, respectively. Synthesis Example 1 (Softening agent 1) 100 parts of glycerin-based propylene oxide (hereinafter abbreviated as PO) / ethylene oxide (hereinafter abbreviated as EO) copolymerized polyether polyol (PO / EO = 20/80, molecular weight = 3000), PO / EO copolymerized polyether polyol (PO / EO = 30/70, molecular weight = 2
000) 33.3 parts and hexamethylene diisocyanate 16.8 parts are mixed and reacted at 100 ° C. for 3 hours,
A urethane prepolymer containing 1.90% free isocyanate was obtained. Next, 6.5 parts of butanone oxime and 45 parts of dioxane were mixed with the urethane prepolymer, and the reaction was carried out at 60 ° C. to confirm that the isocyanate had disappeared, and the blocking was completed. Next, 320 parts of water was mixed to obtain a water-soluble heat-reactive urethane resin having a solid content of 30%.

Synthesis Example 2 (Softening agent 2) Silicone polyol (modified silicone oil manufactured by Toray Silicone, SH-3771, hydroxyl value = 73.
1, 100 parts of a molecular weight of 2300) and 22 parts of hexamethylene diisocyanate were mixed and reacted at 90 ° C. for 90 minutes to obtain a urethane prepolymer containing 4.40% of free isocyanate. Next, 40 parts of ethanol was added at 40 ° C. and mixed for 5 minutes, and then 67 parts of a 20% sodium bisulfite aqueous solution having a concentration of 20% was added and mixed at 35 ° C. to carry out a reaction while stirring at 35 to 45 ° C. for 60 minutes to produce an isocyanate. Was confirmed to have disappeared, and blocking was completed. Next, 223 parts of water was mixed to obtain a water-soluble heat-reactive urethane resin used in the present invention having a solid content of 30%.

Synthesis Example 3 (Softening agent 3) PO / EO copolymerized polyether polyol in ethylenediamine (PO / EO = 20/80, molecular weight = 8000)
After adding 3.8 parts of hexamethylene diisocyanate to 100 parts and carrying out the reaction at 100 ° C. and confirming that the isocyanate groups have disappeared, 420 parts of water were mixed to obtain a solid component 2
A 0% non-reactive water-soluble urethane softener was obtained.

Synthesis Example 4 (Softening agent 4) 100 parts of polyester polyol (butylene adipate, hydroxyl number 110, molecular weight 1000), 2.7 parts of trimethylolpropane and 34 parts of hexamethylene diisocyanate were added and mixed at 50 ° C. 90 ° C thereafter
Was reacted for 90 minutes to obtain a urethane prepolymer containing 5.0% of free isocyanate. Next, 70 parts of ethanol was added at 40 ° C., mixed for 5 minutes, and then 85 parts of a 25% strength sodium bisulfite aqueous solution was added and mixed at 35 ° C. for 35 to 35 minutes.
The reaction was carried out while stirring at 40 ° C. for 90 minutes to complete blocking. Next, 476.8 parts of water was mixed to obtain a solid content of 2
A 0% water-soluble heat-reactive urethane resin was obtained.

(Softener 5) Silicone oil emulsion (manufactured by Wacker Chemicals)

Examples 1 to 4 and Comparative Examples 1 to 4 Each of the softener aqueous solutions was spray-coated on a paper obtained from linter pulp, and then heat-treated at 125 ° C. for 1 minute. The strength and texture of each paper after being processed were evaluated. The results are shown in Table 1.

[0041]

[Table 1]

Examples 5 to 8 and Comparative Examples 5 to 9 Each of the above softener aqueous solutions was spray-coated on the paper obtained from waste paper pulp, and then heat-treated at 125 ° C. for 1 minute. The strength and texture of each paper after processing was judged and the results are shown in Table 2.
Shown in.

[0043]

[Table 2]

Examples 9 to 10 and Comparative Examples 10 to 13 Each of the above softener aqueous solutions was spray-coated on creped paper and then heat-treated at 125 ° C. for 1 minute. The strength of the paper after processing, the texture, and the generation of paper dust were determined, and the results are shown in Table 3.

[0045]

[Table 3]

Examples 11 to 12 and Comparative Example 14 Paper obtained from linter pulp was made into paper, spray-coated, and dried and heat-treated at 150 ° C. for 1 minute with a Yankee dryer. After that, crepe processing was performed on the surface of the drum dryer. The texture, tensile strength, and peeling state of the paper after crepe processing were evaluated, and the results are shown in Table 4.

[0047]

[Table 4]

Each evaluation method is shown below. Tensile strength Test piece size: length x width = 11 cm x
1.5cm Distance between chucks 5cm Dry: Temperature / humidity = 20 ° C / 60% RH Wet: Measured immediately after wetting with the central brush

Folding endurance (number of times / load) Test piece size: length × width = 11 cm × 1.5 cm Load: 1 kg or 0.5 kg KUMAGAI RIKI MIT Folding endurance tester

Bursting strength (kg / cm ² ) YASUDA SEIKI BURSTING STRENGIH TESTER No305-YPL

Texture The feel was judged by the following criteria by 10 panelists, and the average value was taken. ◎: Very soft ○: Soft △: A little hard ×: Hard

Generation of Paper Powder A face is patted 20 times with a processed paper having a size of 10 cm × 10 cm. The degree of the paper dust (pulp) adhering to the face is judged according to the following criteria. Tested by 10 people and averaged. ◎: None at all ○: Almost none △: Slight adhesion ×: Large adhesion

Peeling state of paper during crepe processing ◯: Paper does not peel on the drum surface Δ: Paper tends to peel on the drum surface ×: Paper peels on the drum surface and cannot be creped

[0054]

With the paper softener of the present invention, not only flexibility but also improvement in paper strength is recognized, and also in waste paper, improvement in flexibility and paper strength is recognized. From this,
The applicable range of pulp types used is also wide. On the other hand, softeners using polyester polyols are found to have poor paper strength but poor flexibility, while general water-based softeners and softeners based solely on a non-reactive urethane resin have good flexibility. A decrease in paper strength is observed.

Furthermore, in the creped paper, not only flexibility and strength of paper but also the softening agent of the present invention binds between cellulose fibers, and paper dust is hardly generated, which is extremely useful. Further, after the resin is attached, even if the crepe process is performed, the peeled state of the paper is not seen, and the crepe process can be performed smoothly.

Claims (1)

[Claims] 1. A silicone polyol compound, or a silicone polyol compound and a polyether polyol, and an organic polyisocyanate having two or more isocyanate groups in a molecule and having a terminal isocyanate of 1.0.
A paper softener containing a water-soluble heat-reactive urethane resin as an essential component, which is obtained by blocking the isocyanate group of a urethane prepolymer having a content of ˜6.0 wt% with a blocking agent that regenerates the isocyanate group by heat treatment.