Method for producing vinyl amine unit-containing polymer solution

Abstract

Provided is a method for efficiently producing on an industrial scale a high-performance polyvinylamine solution having good handling properties. After producing a polymer containing N-vinylcarboxamide monomer units having a value of the weight average molecular weight (Mw)/number average molecular weight (Mn) of 5 or higher by aqueous solution standing adiabatic polymerization, the polymer is hydrolyzed in an aqueous solvent in the presence of an alkali and an antigelling agent. In a preferred embodiment of the present invention, a polymer powder having a volatile content of 0.1-12% by mass is obtained by drying and pulverizing after producing a (co)polymer, and the powder obtained is stored or transported to the site of use of the polymer solution and hydrolyzed in an aqueous solvent in the presence of an alkali and an antigelling agent when the polymer solution is needed or at the site of use of the polymer solution.

Claims

1. A method for producing a vinyl amine unit-comprising polymer solution comprising: producing a polymer comprising N-vinylcarboxamide monomer units and having a value of weight average molecular weight Mw/number average molecular weight Mn of at least 5 by an aqueous solution standing adiabatic polymerization method, and then performing hydrolysis on the polymer in an aqueous solvent under the presence of alkali and an antigelling agent.

2. The method according to claim 1, wherein the N-vinylcarboxamide monomer units in the polymer are at least 50 mol % of all monomer units in the polymer.

3. The method according to claim 1, wherein the N-vinylcarboxamide monomer units are N-vinylformamide monomer units.

4. The method according to claim 1, wherein the antigelling agent is at least one selected from the group consisting of dithionite, sulfite, hydrogensulfite, disulfite, sulfoxylate formaldehyde adduct, thioureadioxide and sodium borohydride.

5. The method according to claim 1, wherein reduced viscosity of 0.1 g/dl of the polymer in a 1N brine is 2 to 9.

6. The method according to claim 1, wherein polymer concentration in the aqueous solvent upon performing hydrolysis is at least 3% by mass.

7. The method according to claim 1, wherein polymer concentration in the aqueous solvent is at least 3% by mass.

8. A method for producing the polymer solution according to claim 1, wherein the polymer comprising N-vinylcarboxamide monomer units after being produced by aqueous solution standing adiabatic polymerization, is then dried and powderized to obtain polymer powder having 0.1 to 12% by mass of volatile components, followed by performing hydrolysis on the powder obtained in said aqueous solvent under the presence of said alkali and said antigelling agent.

9. The method for producing a polymer solution according to claim 8, comprising transporting the polymer powder obtained to a location of use of the polymer solution, and performing hydrolysis on the polymer powder in an aqueous solvent under the presence of alkali and an antigelling agent at the location of use.

10. The method according to claim 1, wherein the polymer comprising N-vinylcarboxamide monomer units is a mixture of at least two N-vinylcarboxamide polymers having different reduced viscosities.

11. A retention and drainage aid for papermaking comprising the vinylamine unit-containing polymer solution according to claim 1.

Description

EXAMPLES

(1) Next, the present invention will be explained in further detail by way of examples; however, the present invention is not to be limited to the following examples, so long as not exceeding the spirit thereof. It should be noted that the properties of the (co)polymers of the examples and comparative examples were measured according to the following methods.

(2) (Measurement of Reduced Viscosity)

(3) The (co)polymer sample was dissolved to a 0.1 g/dl concentration as net weight in a 1N brine solution, and the flow-down time was measured using an Ostwald viscometer at 25° C. Similarly, the flow-down time of the 1N brine solution was measured, and the reduced viscosity was obtained according to Formula 1 below.
Reduced Viscosity (η.sub.sp/C)=(t−t.sub.0)/t.sub.0/0.1 [dL/g]  (Formula 1)

(4) t: flow-down time of the sample solution (sec)

(5) t.sub.0: flow-down time of 1N brine (sec)

(6) (Measurement of Polymerization Conversion Rate)

(7) The (co)polymer powder was extracted with methanol and water, and the residual monomer was analyzed employing liquid chromatography. As the main impurities, N-vinylcarboxamide and a water adduct of N-vinylcarboxamide were detected, the total of these were obtained by N-vinylcarboxamide conversion and defined as the residual monomer amount, and by correcting for the volatile component amount obtained separately, the conversion rate was calculated.

(8) (Volatile Component Amount)

(9) The (co)polymer powder was heated for 90 minutes at 105° C., and the decreased amount was obtained by a gravimetric method.

(10) (Measurement of Aqueous Solution Viscosity)

(11) The temperature of the polymer aqueous solution was set to 25° C., and was measured with a Brookfield viscometer at conditions of 6 rpm and rotor No. 4. It should be noted that the viscosity is written as mPa.Math.s.

Example 1

Synthesis and Performance Evaluation of Polymer A: Aqueous Standing Adiabatic Polymerization Method

(12) Polyethylene glycol (average molecular weight: 20000) in an amount of 0.3 parts by mass was dissolved in 70 parts by mass of deionized water, and then mixed with 30 parts by mass of N-vinyl formamide (99 wt % purity). Furthermore, the monomer aqueous solution was adjusted to pH=6.3 with phosphoric acid after the addition of 0.1 parts by mass of sodium acetate to obtain the monomer preparation.

(13) After cooling this monomer preparation to 0° C., it was transferred to an adiabatic reaction vessel equipped with a thermometer and was nitrogen purge for 15 minutes, followed by adding 1500 ppm of 2,2′-azobis(2-amidinopropane)dihydrochloride (tradename: “V-50” manufactured by Wako Junyako Co., Ltd.) and 200 ppm (relative to monomer) of t-butyl hydroperoxide (tradename: “Perbutyl H-69” manufactured by Nippon Oils & Fats Co., Ltd.) as a 10% by mass aqueous solution, and subsequently, 600 ppm (relative to monomer) of ferrous sulfate 7-hydrate was added as a 10% by mass aqueous solution, thereby initiating polymerization.

(14) The highest point for the temperature in the system after 240 minutes from polymerization initiation was confirmed, and subsequently, was held in the reaction vessel for a further 60 minutes. Subsequently, the produced polymer was withdrawn from the reaction vessel to obtain an N-vinyl formamide polymer gel excelling in handling properties.

(15) The N-vinyl formamide gel polymer gel was cut in 3 cm squares, the cut gel segments were processed with a meat chopper having a 4.8 mm die bore to make the gel fragments into particles granulated to no more than 5 mm squares. The obtained gel particles maintained the shape of fine particles, and had favorable handling properties.

(16) Next, the particles were dried for 2 hours at 80° C., and the dried particles were pulverized with a Wiley-type pulverizer to make powder form (particle size of 10 mesh-pass to 100 mesh-on: at least 95%). As a result of measuring the physical properties for the obtained powder of N-vinyl formamide polymer, the reduced viscosity was 7.2 (dl/g), polymerization conversion rate was 99.7%, and the volatile component was 3.2% by mass. In addition, Mw/Mn measured by GPC method was 11.58. Defining this polymer as Polymer A, the below property and performance evaluations of the polymer solution were conducted.

Example 2

Synthesis and Performance Evaluation of Polymer B: Aqueous Solution Standing Adiabatic Polymerization Method

(17) Except for increasing the amount of 2,2′-azobis(2-amidinopropane)dihydrochloride to 2000 ppm, N-vinyl formamide polymer powder with a reduced viscosity of 5.8 dl/g was obtained performing polymerization by the same method as Polymer A. The polymerization conversion rate was 99.8%, and the volatile component amount was 4.5% by mass. Mw/Mn measured by the GPC method was 6.5. Defining this product as Polymer B, the below property and performance evaluations of the polymer solution were conducted.

(18) (Synthesis of Polymer C: Aqueous Standing Adiabatic Polymerization Method)

(19) Except for increasing the amount of 2,2′-azobis(2-amidinopropane)dihydrochloride to 2500 ppm, N-vinyl formamide polymer powder with a reduced viscosity of 3.9 dl/g was obtained performing polymerization by the same method as Polymer A. The polymerization conversion rate was 99.8%, and the volatile component amount was 4.5% by mass. Mw/Mn measured by the GPC method was 5.1. This product was defined as Polymer C.

Example 3

Preparation and Performance Evaluation of Polymer D

(20) The Polymer C and the Polymer A were mixed so as to be 70%/30% by mass, and defined as Polymer D. Upon analyzing Polymer D, the reduced viscosity was 6.4 dl/g, polymerization conversion rate was 99.8%, and the volatile component amount was 4.5% by mass. Mw/Mn measured by the GPC method was 9.1. The below property and performance evaluations of the polymer solution were conducted for this Polymer D.

Comparative Example 1

Synthesis and Performance Evaluation of Polymer E: Photopolymerization Method

(21) A monomer solution was prepared by uniformly dissolving 333.3 g of N-vinyl formamide (99% purity) as the monomer, 0.11 g of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as the initiator, 5.5 g of ammonium chloride, 0.55 g of “SANISOL B50” (benzalkonium chloride-based surfactant manufactured by Kao Corp., 50% purity), 0.055 g of “AF108” (surfactant manufactured by Toho Chemical Industry Co., Ltd.), and 210.5 g of desalted water, then nitrogen gas is supplied hereinto to remove dissolved oxygen.

(22) To the bottom surface of a tray-shaped container (bottom surface 235 mm×235 mm) with a bottom made of stainless steel, a polyethylene terephthalate film (base film 12 μm thick, PVDC coat 4 μm thick) was spread, the monomer solution was placed herein, and the top part was covered with a polyethylene terephthalate film. From above, a fluorescent chemical lamp was irradiated so as to be an intensity of 3 W/m.sup.2 at the irradiated surface. During the irradiation period, 10° C. cold water was sprayed on the stainless steel surfaces of the container to remove the heat of polymerization. The temperature that was 15° C. prior to irradiation reached the highest of 42° C. after 90 minutes. After 120 minutes from irradiation initiation, the irradiation intensity was raised to 6.5 W/m.sup.2, and polymerization was continued for further 60 minutes. An uncolored clear gel of N-vinyl formamide polymer was obtained.

(23) The gel was pulverized with a meat chopper to make particles of about 4 to 5 mm, followed by drying for 2 hours with an 80° C. forced-air drier. Subsequently, it was re-pulverized with a rotating-type pulverizer having a 1-mm φ screen, to obtain powder of the N-vinyl formamide polymer. The volatile component amount was 4.7% by mass, and the polymerization conversion rate was 98.7%. In addition, the reduced viscosity was 11.6 dl/g. Mw/Mn measured by the GPC method was 4.6. Defining this product as Polymer E, the below property and performance evaluations of the polymer solution were conducted.

Comparative Example 2

Synthesis and Performance Evaluation of Polymer F

(24) Except for increasing the amount of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide to 0.55 g, a N-vinyl formamide polymer powder with a reduced viscosity of 8.3 dl/g was obtained by performing polymerization with the same method as Polymer B. The polymerization conversion rate was 99.0%, and the volatile component amount was 4% by mass. Mw/Mn measured by the GPC method was 4.2. Defining this product as Polymer F, the following property and performance evaluations of the polymer solution were conducted.

(25) (Solution Hydrolysis Method)

(26) To a separable flask made of glass having a mixer, 275.2 g of desalted water was placed, and 8.45 g of sodium hydroxide and 0.75 g of sodium dithionite as the antigelling agent were dissolved therein, 15 g of the N-vinylcarboxamide polymer net weight was added gradually under stirring, and after stirring for 1 hour at room temperature, was heated to 50° C. After 2 hours, it was further heated to 80° C., and hydrolysis was carried out while keeping at 80° C. for 2 hours. After cooling, the polyvinylamine solution of the contents was withdrawn. The aqueous solution viscosity of polyvinylamine was measured, and is shown in Table 1.

(27) (Evaluation Methods of Drainage Property and Water Squeezability)

(28) After soaking cardboard in water, the concentration was adjusted by beating for 20 minutes using a beater, and a test slurry with a Canada standard freeness (CFS)=90, 1% concentration and pH 6.91 was obtained. Then, the drainage property was evaluated in the following way. In other words, to 500 ml slurry as the freeness agent, 200 ppm (relative to cardboard) of the polyvinylamine solution as polymer net weight was added, and stirred for 20 seconds at 900 rpm by a paddle blade, then subsequently the drainage amount after 10 seconds was measured with a dynamic drainage tester (Kumagai Riki Kogyo Co., Ltd.). On the other hand, using the same slurry, a papermaking, paper sheet was sandwiched by filter cloth manually using a square-type sheet machine, and by pressing with a press machine for 5 minutes at 0.4 MPa and for a further 2 minutes at 0.4 MPa, then testing the water content ratio in this state, the standard of water-squeezability was established. The results are shown in Table 1.

(29) TABLE-US-00001 TABLE 1 Polyvinylamine aqueous Reduced solution Drainage Water- Polymerization viscosity viscosity property squeezability method Mw/Mn (dl/g) (mPa .Math. s) (ml) (% by mass) Example 1 Polymer A Adiabatic 11.6 7.2 4500 110 78.5 polymerization Example 2 Polymer B Adiabatic 6.5 5.8 2600 105 82.2 polymerization Example 3 Polymer D Adiabatic 9.1 6.4 4000 110 81.1 (Polymer A + Polymer C) polymerization Comparative Polymer E Photopolymerization 4.6 11.6 12000 108 83.0 Example 1 Comparative Polymer F Photopolymerization 4.2 8.3 6000 90 95.0 Example 2

(30) As shown in Table 1, the polyvinylamines produced by hydrolyzing Polymers A, B, D and E show substantially the same drainage property and water-squeezability; however, Polymer E has high solution viscosity and thus poor handling properties. The polyvinylamine produced by hydrolyzing Polymer F has substantially the same handling properties as Polymers A, B and D; however, it is poor from a performance aspect (drainage property and water-squeezability).