CH618993A5 - Process for the preparation of a new water-soluble resin - Google Patents

Abstract

The resin is prepared by reaction of glyoxal with a water-soluble branched poly( beta -alanine). The poly( beta -alanine) is obtained by polymerisation of acrylamide and optionally modified to make it anionic or cationic. The resin thus prepared is used for the treatment of paper, the strength of which it improves.

Description

The invention relates to a process for the preparation of new water-soluble resins. Such resins give paper resistance in the dry state and temporary resistance in the wet state.

It is known to add certain resins to paper, usually during the papermaking process, to improve their wet and / or dry strength. The type of resin added depends on the properties desired in the final paper product. In the case of handkerchiefs or paper towels and for certain other applications, it is desirable that the reinforcing resin added to the paper gives it dry strength and temporary resistance to the wet state.

Many resins are known in this technique which achieve these results. For example, US Pat. Nos. 3,607,622.3,728,214 and 3,778,215 relate to resins which provide both dry strength and temporary wet strength to the paper. These resins are prepared by the reaction of certain polyamines and aminopoly-amides with an acrylamide and then with a polyaldehyde. Likewise, US Pat. No. 3,556,932 describes reinforcement resins in the wet and dry state, which are water-soluble ionic polymers of vinylamide having amide substituents reactive with glyoxal and a sufficient amount of substituents -CHOHCHO to be thermosetting. The polymers are produced by reacting glyoxal with vinylamide polymers, such as ionic copolymers of acrylamide with monomers which impart ionic properties to the polymer, for example diallyl-dimethyl-ammonium chloride and 2-methyl -5-vinyl-pyridine. Vinylamide polymers are produced under conditions which result in polymerization by the addition of acrylamide via the double bond of the vinyl group. After modification with glyoxal, there is a polymer product composed of units having the formulas:

While these resins provide dry strength and temporary wet strength to paper, they have the disadvantage of having a relatively short shelf life when stored in aqueous solution at the concentrations at which typically use them during the papermaking process.

In accordance with the present invention, poly (β-alanine) resins modified with glyoxal which are effective resins for dry strength and temporary wet strength of papers are prepared. These new resins,

which are obtained according to the invention by the process defined in claim 1, are stable in aqueous solution with relatively high solids concentration and have an extended shelf life. These new resins are preferably prepared by (a) polymerization of acrylamide in the presence of a basic catalyst and of a free radical inhibitor to produce a branched water-soluble poly (ß-alanine),

(b) dissolving poly (ß-alanine) in water to provide an aqueous solution with a solids content of from about 11 to about 40% and

(c) adding glyoxal in an amount of about 10 to about 100 mol%, based on the recurring amide units of poly (ß-alanine), thereby producing a glyoxal-modified poly (ß-alanine).

The poly (ß-alanine) used during the preparation of the new resins according to the invention is a water-soluble branched poly (ß-alanine) which can be prepared by anionic polymerization of acrylamide in the presence of a basic catalyst and a vinyl polymerization inhibitor. The anionic polymerization of acrylamide gives rise to a polymer backbone with recurring β-alanine units. The preparation of linear crystalline poly (β-alanine) by anionic polymerization of acrylamide is described in US Pat. No. 2,749,331. Water-soluble and water-insoluble polymer forms are obtained. In this latter reference, it has been determined that the water-soluble form of poly (β-alanine) may be either a linear crystalline polymer of relatively low molecular weight, or a polymer of higher molecular weight having a branched structure. A branched poly (ß-alanine) contains repeating units of formula ~ CH2CH2CONH ~ in the linear segments and repeating units of formula ~ CH2CH2CON ~ in the segments on which branching occurs. Primary amide end groups occur at the end of each branched chain. Hydrolysis of water-soluble branched poly (ß-alanine) produces ß-alanine, NH2CH2CH2COOH, from linear segments of imino-dipropionic acid, NH (CH2CH2COOH) 2 from branching points and ammonia to from terminal primary amide groups.

n / a This provides a basis for measuring the rate of branching present in a given sample of poly (ß-alanine). By hydrolysis of the sample, the ammonia and / or imino-dipropionic acid produced can be measured, which thus provides a determination of the rate of branching. The amount of ammonia-55 released releases the number of primary amide groups and since these groups are present only as terminal groups of the branched chains, an indication of the amount of branching of poly (ß-ala) can be determined. -nine). A poly (β-alanine) containing sufficient branching to be water-soluble is suitable for the application according to the present invention. In general, the branched poly (ß-alanine) should contain about one primary amide group per 2 to 6 amide groups present. The molecular weight of water-soluble branched poly (β-alanine) suitable for the application according to the invention is between approximately 500 and approximately 10,000 and preferably between approximately 2000 and approximately 6000.

As mentioned above, the water-soluble branched poly (ß-alanine) can be prepared by anionic polymerization.

CH2 CH CH2-CH-

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C- O and C O

I I

NH2 NHCHOHCHO

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618,993

as acrylamide in the presence of a basic catalyst and an inhibitor of vinyl polymerization or of free radicals. Due to the extremely exothermic nature of anionic polymerization, it is preferable to carry out the reaction in a suitable organic reaction medium, inert under the reaction conditions and capable of dissolving or suspending the acrylamide. Suitable media include aromatic and aliphatic compounds, for example toluene, xylene, tetrahydronaphthalene, chlorobenzene, nitrobenzene and dioxane.

The concentration of the acrylamide monomer in the reaction medium is between approximately 2 and approximately 30% and preferably from approximately 8 to approximately 15%.

If desired, an organo-soluble polymeric dispersing agent can be added to the reaction mixture prior to the addition of the basic catalyst. When the dispersing agent is used, the poly- (β-alanine) produced is powdery or in the form of pearls, easy to filter from the reaction medium. Suitable dispersing agents are styrene-butadiene copolymers, polyisoprene, chlorinated polypropylene, chlorinated and maleated polyisoprene and chlorinated and maleated polyolefins.

Illustrative examples of basic catalysts which can be used include alkali metals, alkali metal hydroxides, alkaline earth metal hydroxides, quaternary ammonium hydroxides and alkali metal alcoholates. Examples of suitable basic catalysts are metallic sodium, sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium tert-butoxide, sodium methylate, tetran hydroxide. ethyl ammonium, potassium tert-butoxide and calcium hydroxide. The amount of catalyst used is between approximately 0.01 and approximately 2.0 mol%, preferably from approximately 0.1 to approximately 1.5 mol% relative to the monomer.

A free radical inhibitor is added to the reaction mixture to inhibit vinyl polymerization through the double bond of the acrylamide monomer. Examples of free radical inhibitors that can be used are phenyl-ß-naphthylamine, hydroquinone, diphenylamine and phenothiazine.

The anionic polymerization reaction is carried out at a temperature between about 40 and about 140 ° C and preferably from about 80 to about 130 ° C.

In many cases, the anionic polymerization of acrylamide under the above conditions produces a mixture of water-soluble and water-insoluble poly (β-alanine). The water-soluble polymer which can be used according to the present invention can be easily separated by partially dissolving the polymer product in water and removing the insoluble fraction by conventional methods such as filtration, etc.

Poly (ß-alanine) is a neutral polymer. For most (but not all) methods of applying reinforcing resins to paper, the resin must be ionic to achieve effective retention by the pulp. For this reason,

during the preparation of the resins according to the invention, it is desirable to modify the branched, water-soluble poly (β-alanine) before the reaction with glyoxal to introduce anionic or cationic groups into the polymer structure. However, if the resin reinforcement is to be used so that the resin does not need to be ionic, for example by surface application to sheet-shaped paper, the ionic modification of the poly (ß-alanine) before the reaction with glyoxal is not necessary.

An anionic modification of the branched poly (ß-alanine) can be carried out by partial hydrolysis of the polymer, to transform some of the primary amide groups into anionic carboxyl groups. For example the hydrolysis of poly (ß-

alanine) can be carried out by heating a weakly basic aqueous solution of the polymer, the pH of which is approximately 9 to 10 at a temperature of approximately 50 to approximately 100 ° C. The amount of anionic groups introduced should be from about 1 to about 10 mol% and preferably from about 2 to about 5 mol% based on the recurring amide units.

Another method of anionic modification of branched poly (ß-alanine) is treatment with formaldehyde and then with the bisulfite ion.

The cationic modification of the branched poly (ß-alanine) is carried out by reaction of the poly (ß-alanine) in aqueous solution with formaldehyde and dimethylamine. This reaction can be carried out by heating an aqueous solution of the three reactants from approximately 70 ° C. to approximately 80 ° C., either at basic pH from approximately 9 to approximately 11, or at acidic pH from approximately 2 to approximately 4. This reaction introduces tertiary amine end groups into the polymer. When the pH of the resulting aqueous solution is adjusted to apply conditions, that is, from about 4.5 to about 8.0, the tertiary amine groups are protonated and thus are made cationic. The amount of formaldehyde and dimethylamine used is between approximately 2 and approximately 15 mol% relative to the recurring amide units of poly (ß-alanine). The amount of cationic groups introduced is between approximately 2 and approximately 15 mol% and preferably between approximately 4 and approximately 8%

molar compared to recurring amide patterns.

The final step in the preparation of the new resins according to the present invention is the reaction of poly (ß-alanine) with glyoxal. As mentioned previously, poly (ß-alanine) can be modified to introduce anioic or cationic groups as desired, before reaction with glyoxal. The reaction of poly (ß-alanine) and glyoxal takes place in aqueous solution. Solid concentration of poly (ß-alanine)

in the aqueous solution must be greater than approximately 10% and it can be between 11 and approximately 40%, preferably between approximately 12.5 and approximately 25%. The amount of glyoxal used in this reaction can be between approximately 10 and approximately 100 mol% and is preferably between 20 and approximately 30 mol%, relative to the recurring amide units of poly (β-alanine). The reaction temperature is from about 10 to about 50 ° C, preferably from about 20 to about 30 ° C.

The reaction between glyoxal and poly (ß-alanine) is continued until an increase in viscosity from about 2 to about 10, preferably from 4 to 6 viscosity units on the Gardner-Holdt scale has happened. The increase in viscosity indicates that a certain amount of poly (ß-alanine) crosslinking has occurred. The amount of cross-linking is insufficient to cause freezing of the poly (ß-alanine) solution but is capable of providing polymeric units of molecular weight high enough to be retained by the cellulose fibers when used at title of paper reinforcement resin.

The poly (β-alanine) resins modified with glyoxal according to the present invention can be used to impart dry strength and temporary wet strength to paper by applying any conventional method. Aqueous solutions of resin can be applied to the shaped sheet of paper, for example by spraying, or tank application, etc. When applied in this way, the resin need not be ionic. However, the presently preferred methods of incorporating these resins into paper involve adding dilute aqueous solutions of the resins to an aqueous solution of paper pulp before forming sheets. For example, you can add the resin solution to the pulp in the refiner pile, in the pulp tank, the Jordan refiner, the ventilation pump, the head tray or at any other suitable point. Due to the s

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618,993

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anionic nature of cellulose fibers, it is desirable to use an ionic resin so that it can be adsorbed on cellulose fibers. A cationic resin will be directly adsorbed on the cellulose fibers due to the difference in electrostatic charges. When using an anionic resin it becomes necessary to add a cationic bridging agent to fix the anionic resin on anionic cellulose fibers. Thus, when an aqueous solution of an anionic poly (ß-alanine) modified with glyoxal is used in this way, it is necessary to add a cationic bridging agent. Suitable cationic bridging agents include polymeric cationic retention aids, such as amino-polyamide-epichlorohydrin, polyethylene-imine resins, poly (diallyl mine) and poly (dialkoyl methylamine) resins, cationic starch and other highly cationic polymers, natural or synthetic.

The amount of poly (ß-alanine) modified by glyoxal added to the paper to give it dry strength and temporary wet strength is 0.05 to 2% and usually 0.1 to 1% weight relative to the weight of cellulose fibers.

The following nonlimiting examples serve to illustrate the present invention the parts and percentages are by weight unless otherwise indicated.

Example 1

This example illustrates the preparation of an anionic poly (ß-alanine), modified by the glyoxal characteristic of the invention, and its application as dry reinforcing resin and temporary reinforcement in the wet state of the paper.

Part A

350 parts of anhydrous acrylamide, 1.0 part of phenyl-ß-naphthylamine are placed in a 5-liter round bottom flask with three tubes fitted with a paddle stirrer, a thermometer and a condenser. and 3870 parts of chlorobenzene. The mixture is heated to 85-90 ° C, stirring vigorously to melt and partially dissolve the acrylamide. Then 1.0 part of flake sodium hydroxide is added. After an induction period, an exothermic reaction takes place and a polymer separates on the walls of the flask and on the stirrer. Three additional charges of 1.0 part catalyst are added at 30 minute intervals, and the reaction mixture is heated to about 90 ° C for an additional hour. The hot chlorobenzene is decanted and the resulting solid friable polymer is recovered. The polymer is the branched water-soluble poly (ß-alanine).

Part B

A sample of poly (ß-alanine) prepared in Part A is dissolved in water containing 2 mol% of sodium hydroxide (based on the recurring amide units in the polymer) (ß-alanine). The solution is heated to 90-100 ° C for about 30 minutes, with vapor diffusion to remove the ammonia released during the hydrolysis reaction. The resulting solution is then cooled and the pH is lowered to provide a resin containing about 2 mole% of carboxyl groups as measured by potentiometric titration.

Part C

A 15% aqueous solution of anionic poly (ß-alanine) prepared as in part B is added 25% molar (relative to the recurring amide units) of glyoxal in the form of a 40% aqueous solution. The pH of the resulting solution is kept at 9-10 at room temperature until a 4-6 unit increase in viscosity has occurred.

Gardner. Then the solution is quickly diluted with water until a total of 10% solids is obtained and the pH is adjusted to 5.0 with sulfuric acid. The pot life of the resulting resin is more than 6 months, without loss of efficiency.

Part D

The anionic poly (ß-alanine) modified by glyoxal prepared in Part C is evaluated as a dry and wet reinforcing resin in Rayonier bleached kraft pulp. A 3: 1 mixture (dry base) of aqueous solutions of flyoxal-modified poly (ß-alanine) and an amino-polyamide-epichlorohydrin resin (commercially available from Hercules Incorporated under the trademark) is used. “Kymene 557”) as reinforcing resin according to the following process:

Rayonier bleached kraft pulp is threshing in a cyclic refiner until a Schopper-Riegler refining value of 750 cm3 is obtained. Portions of this paste, adjusted to pH 6.5 with sulfuric acid, are added in a distributor of a Noble Wood type sheet forming machine. Reinforcement resin samples are added to the dispatcher in amounts of 0.25,0.5 and 1% solids based on the pulp solids. The dough is then shaped into sheets of approximately 64 mg / m2 of base weight, and dried for one minute at a temperature of 100 ° C. A control sheet is prepared as above, without the addition of reinforcing resin. After conditioning at approximately 24 ° C and 50% relative humidity for 24 hours, the resulting sheets are studied for resistance in the dry state. The sheets are also studied for wet strength after soaking in distilled water for 10 seconds and for 2 hours to show the temporary nature of wet strength. The results are presented in Table I below.

Example 2

This example illustrates the preparation of a characteristic cationic poly (ß-alanine) modified by glyoxal according to the present invention and its application as dry and wet reinforcing resin for paper.

Part A

In an apparatus similar to that described in Part A of Example 1, 20 parts of anhydrous acrylamide, 35 parts of toluene and a trace of plrenyl-β-naphthylamine are placed. Add a sufficient amount of K + ~ Otert-Bu 0.5 m in tert.-BuOH to the mixture, heated under nitrogen to 90-100 ° C to cause the polymerization demonstrated by a significant exothermic reaction and formation of a polymer solid. The resulting mixture is then heated at 100 ° C for 5 hours, the toluene is separated and the solid poly (ß-analine) is dried.

Part B

To a 25% aqueous solution of essentially neutral poly (ß-alanine), prepared in part A, is added each time 7.5 mol% (relative to the recurring amide units) of formaldehyde (in the form of an aqueous solution) and dimethylamine hydrochloride. The pH is adjusted to 9.0-9.5 with an aqueous sodium hydroxide solution and the solution is heated for 20 minutes on a steam bath at 70-80 ° C. The pH is then adjusted again to 6-7. The resulting resin appears to be cationic in its ability to shift the charge of the anionic wood pulp toward electrical neutrality.

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Part C

To a 20% solution in water of the cationic poly (ß-alanine) prepared in part B is added a 25% molar amount of glyoxal in the form of a 40% aqueous solution. The pH of the mixture 9-10 is maintained until an increase of 4 to 6 units in the Gardner viscosity is observed. The total level of solids is then brought to 10% by dilution with water and the pH is adjusted to 4.5-5.0. The stability of the resulting resin with respect to gelation is greater than 6 months.

Part D

The cationic poly (ß-alanine) modified by the glyoxal prepared in part C of the present example is evaluated as dry and wet reinforcing resin by applying the process described in example 1. an aqueous solution of this resin as the sole reinforcing resin. The results are presented in Table I below.

Table I

Evaluation of glyoxal-modified poly (ß-alanine) resins as paper additives

Resin

% added by

Resistance

Wet strength

report

dry: at ia trac

tensile (1)

dough (kg / cm

(kg / cm wide)

(dry base)

wide)

10 sec. 2 ''

2 hr. 3)

None

-

2.995

0.089

0.071

Example 1

0.25

3,548

0.410

0.267

Example 1

0.50

3.887

0.695

0.339

Example 1

1.00

4,297

0.980

0.570

Example 2

0.25

3.477

0.356

0.143

Example 2

0.50

3,584

0.446

0.232

Example 2

1.00

3,441

0.677

0.249

11 Corrected for a basic weight of 18.12 kg / ream

2) Obtained after soaking for 10 seconds in water

3) Obtained after soaking for 2 hours in water

Example 3

This example illustrates the preparation of a characteristic poly (ß-alanine) modified by glyoxal according to the present invention and its application as a reinforcement resin in the dry state or in the temporary wet state for paper.

Part A

In a round bottom flask with 3 tubes fitted with a stirrer 618 993

With the aid of paddles, a thermometer and a condenser, 200 parts of anhydrous acrylamide, 0.44 part of plranyl-β-naphthylamine and 400 parts of anhydrous toluene are placed. The mixture is heated for 30 minutes under a nitrogen atmosphere at 100 ° C with stirring to melt and partially dissolve the acrylamide. 4 parts of 1.2 N potassium tert.-butoxide are then added to the tert.-butanol and the mixture is heated at approximately 90 ° C. for 18 hours. The hot toluene is decanted and the resulting solid polymer is washed with acetone. The polymer is the water-soluble branched poly (ß-alanine).

Part B

As described above, a 30% aqueous solution of neutral poly (β-alanine) is prepared and the mixture is heated to a temperature of 40 to 50 ° C. A 50% molar amount (relative to the amide units in the polymer) of glyoxal is added to this solution in the form of a 40% aqueous solution. The pH of the resulting solution is raised to about 9.5 and kept at room temperature for about 10 minutes, during which time an increase in Gardner viscosity occurs. The solution is then quickly diluted with water to a total of 4% solids and adjusted to pH 5.5 with sulfuric acid.

Part C

The slightly modified neutral poly (ß-alanine) glyoxal prepared in Part B is evaluated as wet and dry reinforcing resins in sheets prepared from 100% Rayonier bleached kraft pulp (18 , 12 kg / ream) The leaves are soaked for 1 minute in a 20% aqueous solution of neutral poly (ß-alanine) modified with glyoxal at pH 6.0. The leaves are then passed through a pinch roller and they are tumble dried at 100 ° C.

The resistance data for the sheets thus treated are compared with those of untreated sheets as indicated below.

Table II

Tensile strength (kg / cm)

wet wet

Dry (10 seconds)

(2 hours)

untreated leaves

3,495 0.160

-

processed leaves

4.333 1.464

0.464

* Corrected tensile strength for a base weight of 18.12 kg / ream

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Claims (5)

618,993 2 1. Process for the preparation of a water-soluble resin, characterized in that a water-soluble branched poly (ß-alanine) is reacted with glyoxal. 2. Method according to claim 1, characterized in that the water-soluble branched poly (ß-alanine) is an anionic poly (ß-alanine) carrying terminal carboxyl groups. 3. Method according to claim 1, characterized in that the water-soluble branched poly (ß-alanine) is a cationic poly (ß-alanine) carrying terminal tertiary amino groups. 4. Method according to claim 1, characterized in that the poly (ß-alanine) is dissolved in water to obtain an aqueous solution having a solids content of 11 to 40% and glyoxal is added in proportion of 10 to 100 mol% relative to the recurring amide units of poly (ß-alanine). 5. Process for the preparation of a water-soluble resin, characterized in that a water-soluble branched poly (ß-alanine) is first prepared by anionic polymerization of acrylamide in the presence of a basic catalyst and a free radical inhibitor, and then the water-soluble branched poly (ß-alanine) is reacted with glyoxal.