CN101805438B - Preparation method and applications of cationic waterborne polyurethane surface sizing agent - Google Patents

Abstract

The preparation method of the cationic waterborne polyurethane of the present invention belongs to the field of organic adhesives. The process route according to the following steps is divided into three stages: the first stage is pre-polymerization, that is, polyols, small molecular hydroxyl monomers, isocyanates and modified monomers are polymerized step by step and free radicals to generate modified polyurethane Prepolymer; the second stage is chain extension, that is, drop hydrophilic chain extension monomer (monomer containing hydrophilic group) into the prepolymer to introduce ionized groups; the third stage is neutralization and emulsification . The invention aims at the above shortcomings of the water-based polyurethane surface sizing agent, and uses a hydrophobic monomer to modify the polyurethane, so that the modified polyurethane emulsion has good water resistance and stability. After the paper is sizing with the product of the invention, the performance of the paper is obviously improved.

Description

Preparation method and application of cationic waterborne polyurethane surface sizing agent

technical field

The invention belongs to the field of organic adhesives, and relates to a preparation method of a cationic waterborne polyurethane surface sizing agent.

Background technique

Sizing is an important link in the papermaking process, it can endow the paper with certain liquid resistance and increase its strength. The sizing process is to use a hydrophobic substance to cover the surface of the paper fiber to form a hydrophobic film, which reduces the free energy of the fiber surface, thereby resisting the diffusion, wetting or penetration of water or other liquids on the fiber surface. The substance with this property is called For sizing agent. There are two methods of sizing, one is to add sizing agent to the pulp before the paper is formed (during beating or batching), which is called in-pulp sizing, and the other is to apply the sizing agent on the surface of the paper after the paper is formed. Apply glue to the surface. Surface sizing can improve the printing performance of paper and board, improve oil resistance, water resistance, durability and abrasion resistance, improve physical strength, reduce or even eliminate the difference between the two sides of the paper.

Surface sizing agents can be divided into natural polymer surface sizing agents and synthetic polymer surface sizing agents. In the 1990s, the amount of starch-based natural polymer surface sizing agents accounted for more than 90% of the total surface sizing agents, but natural starch-based surface sizing agents have poor film-forming properties and unsatisfactory gelatinization fluidity. It is easy to become turbid and form gel, which limits the application of natural starch surface sizing agents. Due to the conversion of acidic papermaking into medium/alkaline papermaking in large quantities, synthetic surface sizing agents can overcome or make up for some shortcomings of medium/alkaline papermaking, such as slow aging, sizing reversal, and low friction coefficient, etc. Economically changing the surface properties of paper can produce high value-added paper grades, which are more and more widely used. Water-based polyurethane (WPU) is a kind of synthetic surface sizing agent. It uses water as the dispersion medium and has the characteristics of good film-forming performance, high bonding strength, wear resistance, cold resistance, flexibility, etc. Strict environmental protection regulations require that it is widely used in plastics, coatings, construction, textiles and other fields, and it has gradually become a research hotspot in the paper industry.

The cationic waterborne polyurethane polymer has -NH-COO- groups and cationic groups on its molecular chain, which has some unique properties. After sizing, the positive charge of cationic polyurethane can be directly combined with the negative charge of the fiber to form on the surface of the fiber. Adhesive film to achieve better sizing effect. German BK, Bayer, BASF and other companies have successively launched cationic waterborne polyurethane products. At present, cationic waterborne polyurethane surface sizing agents have become a research hotspot in papermaking chemicals. However, its high temperature resistance is not good, and its water resistance is poor.

In order to solve this problem, Liu Jianping and Yang Xiaomin of Shaanxi University of Science and Technology in China used toluene diisocyanate (TDI) and glyceryl monostearate as raw materials, and N- Methyldiethanolamine was used as a chain extender, and acetone was used as a solvent to react for 6.5 hours to obtain an aqueous polyurethane emulsion. The effects of raw material NCO/OH value, reaction temperature and time, chain extender dosage and solvent dosage on dairy stability were discussed, and the structure of the emulsion was characterized by TEM and FT-IR. The best synthetic conditions of polyurethane are obtained: the NCO/OH value is between 1.05 and 1.15; the amount of chain extender accounts for 12.5% to 15% of the total; the total reaction time is 6.5 hours. TEM and FT-IR microscopic characterization showed that it was a kind of polyester polyurethane emulsion with amino groups. What this method prepares is the sizing agent in pulp, and used raw material is more expensive, and cost is higher, and the sizing agent in pulp uses more cheap rosin type sizing agent now, so its application is limited.

Liu Jianfu and Xie Yiming wrote the article "Synthesis of Rosin Polyurethane Sizing Agent and Its Application in Papermaking", using toluene diisocyanate (TDI) and esterified rosin to react for 2.5 hours at 70-80°C to synthesize polyurethane prepolymer. Diethanolamine-based chain extension, using sodium bisulfite (APAM) as a capping agent, and finally emulsified to obtain a cationic rosin-type polyurethane emulsion. This kind of sizing agent was applied to sizing in pulp, and the effects of chain extender dosage, PH value and APAM dosage on polyurethane sizing performance were studied. Experiments show that under medium-alkaline conditions, when the amount of sizing agent is 2%, and the amount of APAM is 0.02%, the sizing degree of paper can reach 25s, and it has obvious strengthening effect on paper. However, this method uses sodium sulfite as end-capping, the reaction is difficult to control, and the sizing effect is difficult to meet the requirements of paper products with high sizing degree requirements.

Chinese patent CN 101440152A reports a preparation method of cationic waterborne polyurethane emulsion and its application on surface sizing. This method synthesizes a prepolymer by reacting toluene diisocyanate (TDI), polyester diol and polyethylene glycol at 45-55°C for 0.5-2 hours, and extends the chain with 1,4-butanediol at 60-70°C. -3 hours, use glacial acetic acid to neutralize to form a salt, add water to emulsify under high-speed stirring, and prepare a cationic water-based polyurethane emulsion. However, the emulsion prepared by this preparation method needs to be used in conjunction with aluminum sulfate or polyaluminum, which does not conform to the trend of alkalinization in pulp sizing in the paper industry, and the sizing degree is difficult to meet the requirements of cultural paper, which is still far from practical application. a certain distance.

Chinese patent CN 101654893A reports a preparation method of a cationic polyurethane/cationic styrene-acrylic composite emulsion surface sizing agent. In this method, a prepolymer is synthesized by reacting isophorone diisocyanate, 1,4-butanediol and polyethylene oxide at 60-65°C for 1.5-3 hours, and a butanone solution of a cationic chain extender is added dropwise under stirring. , After the dropwise addition, react at 60-65°C for 3-4 hours, neutralize with a neutralizer to form a salt, add water to emulsify under high-speed stirring, and obtain a cationic polyurethane emulsion. Then add the aqueous solution of styrene, acrylate, cationic monomer, acrylamide and water-soluble azo initiator dropwise to the cationic polyurethane emulsion, and react for 2 to 4 hours to prepare the cationic polyurethane/cationic styrene-acrylic compound emulsion for surface application. Glue. The process of this method is relatively complicated, the synthesis time is long, and the storage stability of the cationic polyurethane/cationic styrene-acrylic composite emulsion is not good, and the emulsion has a large odor.

Contents of the invention

The purpose of the present invention is to provide a preparation method of a cationic surface sizing agent, the prepared cationic water-based polyurethane emulsion, as a surface sizing agent for paper and cardboard, can improve the surface strength, sizing degree and other properties of paper and cardboard .

The process route of the present invention is divided into three stages: the first stage is prepolymerization, that is, polyol, small molecular hydroxyl monomer, isocyanate and modified monomer are gradually polymerized and free radical polymerized to generate modified polyurethane prepolymer ; The second stage is chain extension, that is, adding hydrophilic chain extension monomers (monomers containing hydrophilic groups) dropwise to the prepolymer to introduce ionized groups; the third stage is neutralization and emulsification.

The preparation method of cationic waterborne polyurethane of the present invention is carried out according to the following steps:

1) Preparation of polyurethane prepolymer: dehydrate the polyol at 90°C and 0.08-0.1Mpa vacuum for 1 hour, adjust the prepolymerization temperature at 50-80°C, add measured isocyanate monomer, small molecule hydroxyl monomer, modified The monomer and catalyst are di-n-butyltin dilaurate. During the prepolymerization process, the R value is controlled to be 1.50-3.00, where R refers to the ratio of the total number of moles of NCO groups in the system to the total number of moles of OH groups in the system. The amount of reactive monomers can be adjusted according to the performance of the emulsion and the effect of sizing, and the molecular weight of the prepolymer can be adjusted according to the size of R, so that the polycondensation and free radical polymerization of each substance can be accompanied by grafting and interpenetration, and the synthesis can be adjusted by adding a solvent the viscosity of the prepolymer;

The polyols described therein include polyether polyols, polyester polyols, polyester polyether mixed polyols, etc.; preferably polyoxypropylene diols, polybutadiene diols, acrylate polyols, polyadipic acid Ethylene glycol ester diol, poly-1,6-hexanediol adipate diol, polytetrahydrofluorofuran diol, poly-1,4-butylene adipate diol (PBA), Polyε-caprolactone diol, polycarbonate-1,6-hexanediol ester diol; more preferably polyoxypropylene diol, polyethylene adipate diol, polyadipate-1 , 4-butanediol ester diol, most preferably polyadipate-1,4-butanediol ester diol or polyadipate-1,4-butanediol ester diol and polyoxypropylene diol or a mixture of polytetrahydrofuran diols;

The isocyanate monomers described herein are toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), liquefied MDI, polymethylene polyphenyl polyisocyanate (PAPI), 1,6 - Hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene-dicyclohexyl-4,4'-diisocyanate (H ₁₂ MDI), methylcyclohexyl diisocyanate (HTDI), preferably In toluene diisocyanate (TDI), liquefied MDI, isophorone diisocyanate (IPDI);

Wherein said small molecule hydroxyl monomer is difunctional or trifunctional alcohol, amines, preferably 1,4-butanediol, ethylene glycol, diethylene glycol (diethylene glycol), 2 , 2-dimethylolpropionic acid (DMPA), nitrogen methyldiethanolamine, N, N-dimethylethanolamine, triethanolamine, trimethylolpropane and ethylenediamine, etc.; more preferably diethylene glycol, 1 , 4-butanediol, ethylene glycol, which account for 1% to 5% of the total solid mass;

The modified monomers described herein are glycerides, hydroxyl-terminated silanes, amino-terminated silanes, and modified rosins, preferably esterified rosins, glyceryl monostearate, and hydroxypropyl polydimethylsiloxane Alkane, γ-aminopropyltriethylaminosilane, which accounts for 1% to 10% of the solid mass;

Wherein said solvent is 1-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, butanone, acetone, toluene, preferably 1-methyl-2-pyrrolidone or acetone, wherein the solvent Accounting for 1-10% of the total solid mass.

2) Chain extension: On the basis of the first step, lower the prepolymer to 30-60°C, and drop a certain amount of hydrophilic chain extender into the bottle at a uniform speed, wherein the hydrophilic chain extender uses a solvent Dilute to a mass fraction of 20% to 40%, and the solvent used is the same as step 1. After the drop, when the R value reaches the theoretical value, proceed to the next step of reaction;

Wherein said hydrophilic chain extender is difunctional or trifunctional alcohol, amines, preferably 1,4-butanediol, ethylene glycol, diethylene glycol (diethylene glycol), nitrogen Methyldiethanolamine, N, N-dimethylethanolamine, triethanolamine, trimethylolpropane and ethylenediamine, etc.; more preferably nitrogen methyldiethanolamine, N, N-dimethylethanolamine and triethanolamine, which Accounting for 4% to 16% of the total solid mass.

3) Neutralization and emulsification: On the basis of the second step, add a neutralizing agent to neutralize the salt formation, and the neutralization degree is 80% to 120%. After 30 minutes, disperse the measured aqueous solution in the modified In the polyurethane prepolymer, the solid content is controlled at 10% to 45%, and stirred at high speed for 30 minutes to obtain a cationic water-based polyurethane surface sizing agent with a light yellow or milky white translucent appearance;

Wherein said neutralizing agent is glacial acetic acid, dilute hydrochloric acid, dilute sulfuric acid, dimethyl sulfate etc.; Preferably in glacial acetic acid, dilute hydrochloric acid, wherein neutralizing agent accounts for PU (PU is except water and solvent total material) material quality 2% to 7%.

The invention aims at the above shortcomings of the water-based polyurethane surface sizing agent, and uses a hydrophobic monomer to modify the polyurethane, so that the modified polyurethane emulsion has good water resistance and stability. After the paper is sizing with the product of the invention, the performance of the paper is obviously improved.

Example

The following examples serve to illustrate the invention, but in no way limit the scope of the invention.

Comparative example: Add 7.5g of polyadipate-1,4-butylene glycol ester diol (PBA) and 4.17g of polyoxypropylene diol (N210) into a three-necked flask, mix and stir, and keep the temperature in a water bath at 90°C Heating, vacuuming and dehydration for 1h, the vacuum degree is 0.098Mpa. Cool down to 70°C, add 5.68g TDI, 0.58g diethylene glycol (DEG), 2g 1-methyl-2-pyrrolidone (NMP) and 0.12g catalyst di-n-butyltin dilaurate until the NCO value in the system basically reaches the theoretical value When the value is high, the prepolymer is obtained, and then the temperature is lowered to 55°C, and 2.00 g of the hydrophilic chain extender nitrogen-methyldiethanolamine (diluted with acetone to a mass fraction of 30%) is added dropwise at a uniform speed. Value, dilute with acetone (about 2 ~ 4g), reduce the viscosity, slowly add 1.20g glacial acetic acid to neutralize ionization (neutralization degree is 120%, neutralization degree refers to the mole of neutralizing agent and hydrophilic chain extender ratio) to react for 0.5h; finally add 70.44g of water under high-speed stirring, and react for 0.5h to obtain a milky white emulsion with a theoretical solid content of 25%.

Example 1: Under the operating conditions of the comparative example, add 1.0 g of hydroxypropyl polydimethylsiloxane (8427) to the three-necked flask before vacuumizing, and finally add 53.79 g of water to obtain a theoretical solid content of 30%. , Pale yellow translucent emulsion.

Example 2: Under the operating conditions of the comparative example, add 0.5 g of glyceryl monostearate to the three-necked flask before vacuumizing, and finally add 44.53 g of water to obtain a milky white translucent emulsion with a theoretical solid content of 35%.

Embodiment 3: under the operating condition of embodiment 1, change 5.68gTDI into 7.25g IPDI, add 0.1mol/L dilute hydrochloric acid 1.28g (neutralization degree is 80%) when neutralizing, add 225.05g water at last, get Theoretical solid content is 10%, colorless translucent emulsion.

Embodiment 4: under the operating condition of embodiment 2, change 5.68gTDI into 8.85gMDI, add 34.57g water at last under high-speed stirring, react 0.5h, obtain theoretical solid content and be 40%, obtain yellow translucent emulsion.

Example 5: Under the operating conditions of Example 1, 0.58g DEG was replaced with 0.34g ethylene glycol, and finally 78g of water was added under high-speed stirring, and the reaction was 0.5h to obtain a theoretical solid content of 23.5%. Transparent lotion.

Embodiment 6: Under the operating condition of embodiment 2, 7.50g polyadipate-1,4-butylene glycol ester diol (PBA) is changed into 7.56g polyε-caprolactone diol (PCL220), The hydrophilic chain extender added dropwise at a constant speed was replaced by 2.3 g of triethanolamine, and finally 40.59 g of water was added to obtain a pale yellow translucent emulsion with a theoretical solid content of 37%.

Example 7: Under the operating conditions of Example 1, 4.17g polyoxypropylene diol (N210) was replaced with 3.72g polytetrahydrofuran diol (PTMG1000), and the hydrophilic chain extender nitrogen-formazan was added dropwise at a constant speed Diethanolamine (diluted with acetone to a mass fraction of 30%) 2.4g, and finally add 168.21g of water to obtain a colorless translucent emulsion with a theoretical solid content of 12.5%.

Embodiment 8: Under the operating condition of embodiment 1, polyadipate-1,4-butylene glycol ester diol (PBA) is changed into 12.5g by 7.5g, and polyoxypropylene diol (N210) is changed by 4.17 g was changed to 1.39g to obtain a light yellow translucent emulsion with a theoretical solid content of 26.7%.

Example 9: Under the operating conditions of Example 7, the preparation temperature of the prepolymer was changed to 55° C., and the chain extension temperature was changed to 40° C. to obtain a colorless translucent emulsion with a theoretical solid content of 20%.

Cationic waterborne polyurethane sizing agent sizing effect test:

A cationic starch solution with a mass fraction of 2.5% is gelatinized at 90°C for 15 to 30 minutes, a certain amount of sample emulsion is taken, and the two are mixed evenly at a dry-dry ratio of 90:10 to make a sizing emulsion. Use this sizing emulsion to carry out surface sizing on the double-offset paper with a quantitative weight of 85g/m ² , and the sizing experiment on the double-offset paper adopts the manual sizing method. First fix one end of the base paper, take a certain amount of sizing agent and apply it evenly on the fixed end, roll it on the paper with a glass rod at a constant speed, so that the sizing agent is evenly applied on the paper surface, and put the sized paper on the Put it into a photo dryer for drying, and finally place the sample after sizing under constant temperature and humidity conditions for 24 hours, and then perform physical performance testing.

The prepared cationic waterborne polyurethane surface sizing agent has a good sizing effect, and when the amount of the sizing agent is 0.1%, the sizing degree of the paper sheet reaches 61 seconds. The surface sizing effect is shown in the table below.

Sizing effect test:

example Exterior Sizing degree/s BaiDu Cobb60/g/ ^m2 comparative example milky white 19 85.9% 67.5 Example 1 Light yellow translucent 61 81.6% 45.01 Example 2 Milky white translucent 62 82.4% 48.58

Example 3 Colorless translucent 49 84.8% 51.21 Example 4 yellow translucent 57 80.7% 39.21 Example 5 light yellow translucent 60 82.8% 40.39 Example 6 light yellow translucent 58 81.2% 41.10 Example 7 Colorless translucent 56 86.4% 42.46 Example 8 yellow translucent 59 80.4% 40.01 Example 9 Colorless translucent 50 85.2% 43.11

Claims (4)

1. the preparation method of cation aqueous polyurethane is characterized in that being undertaken by following step:

1) preparation of base polyurethane prepolymer for use as: with the polyvalent alcohol 1h that under 90 ℃, 0.08～0.1MPa vacuum tightness, dewaters; Regulate 50～80 ℃ of pre-polymerization temperature; The isocyanate-monomer, micromolecular hydroxyl monomer, modified monomer and the catalyzer di-n-butyltin dilaurate that add metering, control R value is 1.50～3.00 in the prepolymerization reaction process; The ratio of the mole number of total OH group in the R mole number that refers in the system total NCO group and the system wherein; The dosage of modified monomer is regulated according to emulsion property and sizing efficiency; According to R size adjustment prepolymer molecular weight; Make each material generation polycondensation and radical polymerization follow grafting, IPN simultaneously, regulate the viscosity of synthetic middle prepolymer through adding solvent;

Wherein said isocyanate-monomer is tolylene diisocyanate (TDI), liquefied mdi or isophorone diisocyanate (IPDI);

Wherein said micromolecular hydroxyl monomer is 1,4-butyleneglycol, terepthaloyl moietie, glycol ether (glycol ether), 2,

2-dimethylol propionic acid (DMPA), N methyldiethanol amine, N, N-dimethylethanolamine, trolamine, TriMethylolPropane(TMP) or quadrol; It accounts for 1%～5% of total solids quality;

Wherein said modified monomer is esterified rosin or glyceryl monostearate, and it accounts for 1%～10% of solid masses;

Wherein said solvent is 1-Methyl-2-Pyrrolidone (NMP), and wherein solvent accounts for 1～10% of solid total mass;

2) chain extension: on the basis of the first step; Performed polymer is reduced to 30～60 ℃; At the uniform velocity in bottle, drip the hydrophilic chain extender of certain metering, it is 20%～40% that wherein said hydrophilic chain extender uses solvent cut to massfraction, and solvent for use is with step 1; After dripping off,, the R value descends the step reaction when reaching theoretical value;

Wherein said hydrophilic chain extender is 1,4-butyleneglycol, terepthaloyl moietie, glycol ether (glycol ether), N methyldiethanol amine, N, and N-dimethylethanolamine, trolamine, TriMethylolPropane(TMP) or quadrol, it accounts for 4%～16% of total solids quality;

3) neutralization and emulsification: on the basis in second step; Add in the neutralizing agent and salify, after degree of neutralization is 80%～120%, 30 minutes; In the modified polyurethane prepolymer of water-dispersion behind salify with metering; The control solid content is 10%～45%, and high-speed stirring 30 minutes, obtains outward appearance and is yellowish or the translucent cationic waterborne polyurethane surface sizing agent of oyster white;

Wherein said neutralizing agent is Glacial acetic acid min. 99.5 or Hydrogen chloride; Wherein neutralizing agent accounts for 2%～7% of PU quality of material; Wherein said polyvalent alcohol comprises polyoxypropyleneglycol, polybutadiene diol, polyethylene glycol adipate glycol, gathers hexanodioic acid-1; 6-pinakon esterdiol, polytetrahydrofuran diol, gather hexanodioic acid-1; 4-butanediol ester glycol (PBA), poly-epsilon-caprolactone glycol or polycarbonate-1,6-pinakon esterdiol.

2. the preparation method of cation aqueous polyurethane according to claim 1; It is characterized in that wherein said polyvalent alcohol is polyoxypropyleneglycol, polyethylene glycol adipate glycol or gathers hexanodioic acid-1; 4-butanediol ester glycol; Wherein said micromolecular hydroxyl monomer is glycol ether, 1,4-butyleneglycol or terepthaloyl moietie.

3. the preparation method of cation aqueous polyurethane according to claim 1, the wherein said hydrophilic chain extender of its characteristic is N monomethyl diethylolamine, N, N-dimethylethanolamine or trolamine.

4. the preparation method of cation aqueous polyurethane according to claim 1; It is characterized in that wherein said polyvalent alcohol is for gathering hexanodioic acid-1; 4-butanediol ester glycol or gather hexanodioic acid-1, the mixture of 4-butanediol ester glycol and polyoxypropyleneglycol or polytetrahydrofuran diol.