CH618474A5 - Process for the preparation of hydrophilic polyolefin fibres - Google Patents

Abstract

Fibres of hydrophilic polyolefin bearing carboxyl groups are produced by discharge spraying. Such fibres are employed as a mixture with wood pulp for paper manufacture. The invention consists in treating these polyolefin fibres in an aqueous mixture of anionic and cationic nitrogenous polymers in order to improve the tensile strength of the paper produced. The cationic polymer is especially a product of reaction of epichlorohydrin and of an aminopolyamide or of a polyalkylenepolyamine and the ionic polymer is especially a product of reaction of glyoxal and of a polyacrylamide containing acrylic acid units.

Description

The present invention relates to a process for preparing hydrophilic polyolefin fibers which are readily dispersible in water and which can be mixed with wood pulp fibers to provide a pulp which can be made into high quality paper by applying conventional papermaking techniques. More particularly, the present invention relates to the formation of polyolefin-based fibers containing carboxylic functions and the treatment of these fibers with mixtures of certain water-soluble polymers containing nitrogen, one of which is cationic and the other is anionic. The present invention also relates to specific mixtures of these anionic and cationic polymers.

In recent years, considerable effort has been made to develop fibrous polyolefin pastes with hydrophilic properties. A process developed with the aim of achieving these hydrophilic properties is that described in US patent no. 3,743,570, on behalf of Crown Zellerbach Corporation. According to this patent, polyolefin fibers with a large specific surface are treated with a hydrophilic colloidal polymer adjuvant, composed of a cationic polymer such as melamine-formaldehyde, and an anionic polymer such as carboxymethyl-cellulose. Another process developed for the preparation of hydrophilic polyolefin pastes is that which involves the spray projection of a mixture of polyolefin and an adjuvant such as a hydrophilic clay or a hydrophilic polymer, for example polyvinyl alcohol . The discharge spraying process applied in these preparations is that in which the polyolefin and the hydrophilic adjuvant are dispersed in a liquid which is not a solvent for either of the components at its normal boiling point. , the resulting dispersion is heated to a pressure higher than that of the atmosphere to dissolve the polymer and an adjuvant possibly present, soluble in the solvent and then the resulting composition is discharged in a zone of lower temperature and pressure, usually those of l atmosphere to form the fibrous product.

A major shortcoming of these hydrophilic polyolefin pulps has been that, when mixed with wood pulp, the resulting paper products exhibit considerably lower resistance than that of paper prepared from wood pulp only . However, some improvement in the strength of paper made from a blend of polyolefin pulp and wood pulp has been achieved by imparting an anionic character to the polyolefin pulp. For example in German patent application no. 2,413,922, on behalf of Toray Industries Inc., describes the preparation of anionic pastes by discharge projection of mixtures of polyolefins and copolymers of olefinic compounds with maleic anhydride or acrylic or methacrylic acids. Mixtures of these pulps with wood pulp provide a paper with better tensile strength than a paper produced without the polymer component.

One of the aims of the present invention is to prepare hydrophilic polyolefin fibers allowing the production of a paper having further improved strength properties, from mixtures of polyolefin pulps and wood pulp. The process for preparing hydrophilic polyolefin fibers according to the present invention is defined in claim 1 above.

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As an example of the process according to the present invention, polypropylene and an acrylic acid-ethylene copolymer are dispersed in a solvent such as methylene chloride, and the dispersion is heated in a closed system to a temperature of approximately 190 °. C, to dissolve the polymer components in the solvent. Under these conditions, the pressure generated by the methylene chloride vapors is of the order of 42.0 kg / cm2. After introduction of nitrogen to increase the vapor pressure of the system to a pressure of about 70.0 kg / cm 2, the discharge of the resulting solution is produced in the atmosphere through an orifice, giving rise to the evaporation of the chloride. methylene solvent and the formation of the fibrous product. The fibrous product is then suspended in an aqueous medium formed by mixing a dilute aqueous solution for example of poly (diethylene-triamine-adipic acid) modified by epichlorohydrin with a dilute aqueous solution for example of poly (acrylamide- co-acid-acrylic) modified by glyoxal, and the components of the resulting suspension are brought into intimate contact, such as by refining in a disc refining apparatus. The treated fibers can then be isolated and stored as a wet cake, or the suspension containing the fibers can be used directly in the papermaking process.

After having sketched in a general manner the forms of implementation of the present invention, the examples which will follow constitute specific illustrations thereof. All quantities are based on weight parts.

Example A

A cationic, water-soluble, nitrogen-containing polymer is prepared from diethylene triamine, adipic acid and epichlorohydrin. Diethylene triamine was added in an amount of 0.97 mole to a reaction vessel fitted with a mechanical stirrer, a thermometer and a reflux condenser. One mole of adipic acid is then gradually added to the reaction vessel with stirring. After dissolving the acid in the amine, the reaction mixture is heated to 170-175 ° C and kept at this temperature for 1 h V2, after which the reaction mixture becomes very viscous. The reaction mixture is then cooled to 140 ° C and an amount of water sufficient to provide the resulting polyamide solution with a solids content of about 50% is added. It is found that a polyamide sample isolated from this solution has a reduced specific viscosity of 0.155 deciliter per gram, measured at a concentration of 2% in a 1 M aqueous ammonium chloride solution. The polyamide solution is diluted to a solid content of 13.5% and the mixture is heated to 40 ° C., and the epichlorohydrin is slowly added in an amount corresponding to 1.32 mole per mole of secondary amine in the polyamide. The reaction mixture is then heated to a temperature between 70 and 75 "C until a Gardner viscosity of E-F is reached. A sufficient amount of water is then added to provide a solids content of about 12 , 5%, and the solution is cooled to 25 ° C. The pH of the solution is then adjusted to 4.7 with concentrated sulfuric acid. The final product contains 12.5% of solids and its Gardner viscosity is B ^ C.

Example B

Another representative cationic, water-soluble, nitrogen-containing polymer is prepared, this time using epichlorohydrin and a commercially available liquid mixture of polyamines as reactants. This mixture contains at least 75% of bis- (hexamethylene) -triamine and higher homologs, the complement of the mixture being constituted by lower molecular weight amines, nitriles and lac-tames. The reaction is carried out in a container provided with a vacuum jet jet system used for the outlet of the vapors by a condenser, instead of allowing their escape through an open orifice in the container.

The container is loaded with 704 parts of water and 476 parts of epichlorohydrin and then 420 parts of the industrial polyamine mixture are added to the container, in a period of 35 minutes, while cooling the reaction mixture to prevent the temperature from exceeding 70 ° C. After the addition of amine, 6 parts of 20% aqueous sodium hydroxide are added to accelerate the reaction and, after a total of 160 minutes at approximately 70 ° C, the reaction mixture is diluted with 640 parts of water to lower the viscosity to a Gardner value of approximately C. A total of 44 parts of 20% aqueous sodium hydroxide is then added over a period of 105 minutes. A Gardner viscosity of S is reached after 215 minutes, the reaction then being completed by the addition of 26 parts of concentrated sulfuric acid dissolved in 1345 parts of water. The resulting solution has a Gardner viscosity of D; additional sulfuric acid and water are added to adjust the pH to

4 and provide a solids content of 22.5%.

Example C

Another cationic, water-soluble, nitrogen-containing polymer is prepared, the basic reagents being the methyl-diallyl-amine of epichlorohydrin. 290 to 295 parts of concentrated hydrochloric acid are slowly added to 333 parts of methyl-diallylamine, to give a solution with a pH of 3 to 4. Then nitrogen is diffused into the solution for 20 minutes and the mixture is adjusted. the temperature at 50 to 60 ° C. A 10.7% aqueous solution of sodium bisulfite and a 10.1% aqueous solution of tert-butyl hydroperoxide are simultaneously added to the reaction mixture in a period of 4 to

5 hours, until the resulting polymer, the poly (methyl methyl diallylamine orhy-drate) has a specific viscosity reduced by 0.2 as measured on a 1% solution in sodium chloride in solution aqueous 1 M at 25 ° C. The amount of sodium bisulfite and tert.-butyl hydroperoxide used is for each of 2 mol% relative to the repeating units of the polymer.

600 parts of 4% aqueous sodium hydroxide are then added to the above polymer solution, and the temperature of the resulting solution is adjusted to 35 ° C. After adding a sufficient amount of water to bring the solids content of the polymer solution to 22%, 416.3 parts of epichlorohydrin are added. The temperature of the reaction mixture is maintained at approximately 45 ° C, while the Gardner viscosity of the mixture increases from less than A to B +. After the addition of about 304 parts of 36% hydrochloric acid, the reaction mixture is heated to 80 ° C and kept at this temperature with the continuous addition of additional hydrochloric acid until the pH of the reaction mixture has stabilized at 2 for one hour. The reaction mixture is then cooled to 40 ° C, the pH is adjusted from 3.5 to 4.0 with a 4% aqueous solution of sodium hydroxide and diluted to 20% solids.

The resin product from the previous process must be activated by a base before use in accordance with the present invention. This is done by adding 18 parts of water and 12 parts of a 1 M sodium hydroxide solution per 10 parts of 20% solids resin solution. The resulting 5% solids solution, after aging for 15 minutes, should have a pH of 10 or higher. Additional sodium hydroxide must be added, if necessary, to achieve this pH level.

Example D

Another useful, cationic, water-soluble, nitrogen-containing polymer is prepared from bis- (3-aminopropyl) -methylamine, urea and epichlorohydrin. We place in a

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reaction vessel 210 parts of amine and 87 parts of urea, the mixture is heated to 175 ° C., it is maintained at this temperature for one hour and then cooled to 155 ° C. Water is added to the reaction product, in an amount of 375 parts, and the resulting solution is cooled to room temperature.

To 271 parts of the above solution, 321 parts of water, 29 parts of concentrated hydrochloric acid and 89.6 parts of epichlorohydrin are added. The temperature of the reaction mixture is maintained between 39 and 42 ° C for about 85 minutes, while the Gardner viscosity increases from A-B to L +. 60 parts of concentrated hydrochloric acid are then added to the mixture, and the resulting mixture is heated for 4 hours at a temperature between 60 and 75 ° C., adding an additional 9 parts of hydrochloric acid after approximately 1 h V2, to preserve the pH below 2. The mixture is then cooled to room temperature. The resulting polyamino-urylene product modified with epichlorohydrin contains 27% solids.

The above product must also be activated by a base prior to use according to the present invention. Activation is carried out by adding 10 parts of the above product to 10 parts of a 1 M sodium hydroxide solution, the resulting solution is allowed to age for 15 minutes, and the solution is then diluted (13.5% solids) to 5% or less solids for application.

Example E

An anionic, water-soluble, nitrogen-containing polymer is prepared from acrylamide, acrylic acid and glyoxal. 890 parts of water are added to a reaction vessel fitted with a mechanical stirrer, a thermometer, a reflux condenser and an adapter for nitrogen, then dissolved in water 98 parts of acrylamide, 2 parts of acrylic acid and 1.5 parts of aqueous cupric sulfate Nitrogen is made to diffuse into the resulting solution and the mixture is heated to 76 ° C., to which point 2 parts of ammonium persul-fate dissolved in 6.5 parts of water are added. increases by 21.5 ° C within 3 minutes of adding the persulfate. When the temperature returns to 76 ° C, it is kept there for 2 hours, after which the reaction mixture is cooled to the temperature The resulting solution has a Brookfield viscosity of 54 centipoise at 21 ° C and contains less than 0.2% acrylamide, based on the t in polymer.

To 766.9 parts of the above solution (76.7 parts of polymer containing 75.2 parts, ie 1.06 mol, of recurring amide units), 39.1 parts of 40% aqueous glyoxal are added (15 , 64 parts, or 0.255 equivalent of glyoxal compared to the recurring amide units). The pH of the resulting solution is adjusted to 9.25 by the addition of 111.3 parts of 2% aqueous sodium hydroxide. Within approximately 20 minutes after the addition of sodium hydroxide, the Gardner viscosity of the solution increased from A and E. The reaction was then completed by the addition of 2777 parts of water and about 2.6 parts 40% aqueous sulfuric acid. The resulting solution has a pH of 4.4 and contains 2.2% solids.

Example F

Another representative anionic, water-soluble, nitrogen-containing polymer is prepared using only acrylamide and glyoxal as reagents. 350 parts of acrylamide, one part of phenyl-beta-naphthylamine and 3,870 parts of chlorobenzene are placed in a reaction vessel fitted with a stirrer, a thermometer and a reflux condenser. This mixture is heated from 80 to 90 ° C with vigorous stirring, to partially melt and partially dissolve the acrylamide. A portion of sodium hydroxide in flakes is then added to the mixture and, after an induction period, an exothermic reaction and separation of polymer takes place on the stirrer and on the walls of the reaction vessel. An additional three batches of 1 part sodium hydroxide flakes are added at 30 minute intervals to the reaction mixture, after which the reaction mixture is heated to about 90 ° C for 1 hour. The hot chlorobenzene is then decanted and the residual solid, a water-soluble branched poly (beta-alanine), is washed three times with acetone and then dissolved at room temperature in 1000 parts of water. The cloudy solution thus obtained, whose pH is approximately 10.5, is heated at approximately 75 ° C for approximately 30 minutes to effect partial hydrolysis of the amide groups of the poly (beta-ala-nine) and blown live steam in the solution until the residual chlorobenzene has been removed and the last traces of polymer have dissolved. After cooling, the solution is adjusted to a pH of about 5.5 with sulfuric acid. The dissolved polymer contains about 2 mol% of carboxyl groups, as determined by potentiometric titration.

To a 15% aqueous solution of the above polymer is added a 40% aqueous solution of glyoxal in an amount sufficient to provide 25 mol% of glyoxal relative to the recurring amide units in the polymer. The pH of the resulting solution is slowly raised to approximately 9.0-9.5 at room temperature by addition of dilute aqueous sodium hydroxide, and the pH is held at this level until an increase Gardner viscosity of 5 to 6 units has occurred. The solution is then rapidly diluted with water for a total of 10% solids and adjusted to pH 5.0 with sulfuric acid.

Example 1

90 parts of isotactic polypropylene, whose intrinsic viscosity is 2.1, are loaded into decahydronaphthalene at 135 ° C., and 10 parts of a copolymer of ethylene and acrylic acid (marketed by DOW, 92: 8 ethylene: acrylic acid, melt flow index 5.3), in a closed autoclave and 400 parts of methylene chloride as solvent. The contents of the autoclave are stirred and heated to 220 ° C., the vapor pressure in the autoclave then being brought to 70 kg / cm 2 by introduction of nitrogen. The resulting solution is sprayed out of the autoclave into the atmosphere through an orifice 1 mm in diameter and 1 mm in length, giving rise to the evaporation of the methylene chloride and to the formation of the desired fibrous product. This fibrous product is refined for 6 minutes in a disc refining device of the type sold by Sprout Waldron, until a consistency of 0.25% is obtained in an aqueous medium containing 0.1% of a mixture of cationic polymer. of Example A and of the anionic polymer of Example E, the weight proportion between the cationic polymer and the anionic polymer being in the resin mixture of 1: 5. The refined fibrous product, after washing with water, contains 8.5% of fixed resin, according to the nitrogen analysis.

Example 2

The fibrous product projected by discharge is refined as in Example 1, except that an aqueous medium containing 0.05% of the mixture of cationic and anionic polymers is used. The refined fibrous product after washing with water contains 5.2% of resin fixed according to the nitrogen analysis.

Example 3

The process of Example 1 is repeated, except that the following conditions are applied in the preparation of fibrous product sprayed by discharge: 95 parts of polypropylene, 5 parts of copolymer of ethylene and of acrylic acid (DOW, 88:12 ethylene: acrylic acid, melt flow index 7.0), a mixture of 360 parts of

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methylene and 40 parts of acetone as solvent, a temperature of 220 ° C and a pressure of 84 kg / cm2. The fibrous product thus obtained, after refining on a disc such as in Example 1, contains 9.0% of deposited resin as determined by nitrogen analysis.

Example 4

The process of Example 1 is repeated again, except that the following conditions are applied this time during the preparation of the fibrous product sprayed by discharge: 90 parts of an isotactic polypropylene having an intrinsic viscosity of 1.3 in decahydronaphthalene at 135 ° C, 10 parts of ethylene-acrylic acid copolymer (Union Carbide, 94: 6 ethylene: acrylic acid), 900 parts of methylene chloride as solvent, a temperature of 200 ° C and a pressure 70 kg / cm2. The fibrous product obtained by this discharge spraying process is then refined on disk, as in Example 1, giving fibers containing 7.2% of fixed resin, according to the nitrogen analysis.

Example 5

A fibrous product sprayed is prepared according to the process of Example 1, except that 80 parts of polypropylene, 20 parts of ethylene-acrylic acid copolymer from Example 4,400 parts of methylene chloride, are used. 210 ° C and a pressure of 70 kg / cm2. The product is refined on disk as in Example 1, giving a fibrous product containing 6.7% of resin deposited according to the nitrogen analysis.

Examples 6 and 7

The repetition of Example 5 is carried out, under identical conditions, except that a weight proportion of 1: 7 is used between the cationic polymer of Example A and the anionic polymer of Example E, in the mixture of resin of Example 6, and a weight proportion of 1: 3 of the polymers of Example 7. The resin absorbed in the fibrous product of Example 6 is 6.5% and 5.1% in the fibrous product of Example 7.

Example 8

Each of the synthetic pulps prepared as described in Examples 1 to 7 is mixed with bleached wood pulp for kraft paper (50:50, RBK: WBK, pH 6.5, 500, according to the so-called “Canadian Standard Freeness” units ») In proportion to 30% synthetic pulp for 70% wood pulp. The leaves prepared from the mixtures are dried and calendered to around 90 kg per running cm at 60 ° C. The gloss, opacity, tensile strength and Mullen resistance to bursting of the calendar sheets are determined, and the results are given in Table I. In the data provided by the table, the tensile strength and the Mullen burst strength are values expressed as a percentage of the tensile strength and Mullen burst strength of a 100% wood pulp control, all corrected for a basis weight of 18 , 12 kg per oar.

Table I

Example

Shine

Opacity

Resistance

Resistance

tensile

to burst

(%)

(%)

(%)

(%)

î

87.3

85.8

90

86

2

87.9

87.2

82

84

3

87.6

87.7

78

78

4

84.4

81.5

71

68

5

87.2

82.5

78

72

6

87.4

81.8

76

76

7

87.5

82.8

79

63

It appears from the above data that the method according to the invention provides a paper having between about 70 and about 80% of the tensile strength and between about 60 and about 85% of the Mullen burst strength a paper prepared from 100% wood pulp.

Example 9

The process of Example 1 is followed, using 200 parts of crystalline polypropylene grafted with 3% by weight of maleic anhydride, 2672 parts of methylene chloride, a temperature of 200 ° C and a pressure of 70 kg / cm2. The fibrous product sprayed by discharge is refined on disc as in Example 1, giving fibers containing 2.7% of deposited resin. The refined paste is mixed with wood pulp and sheets are prepared and evaluated as in Example 8. The resulting sheets have a gloss of 82%, an opacity of 80%, a tensile strength of 67% and 71% burst resistance to bursting.

Example 10

The process of Example 1 is applied to prepare a fibrous product sprayed by discharge from crystalline polypropylene grafted with 6% by weight of acrylic acid. As a dispersing medium, a 3: 2 mixture in proportion by weight of water and hexane is used. The fibrous product is refined on disk as in Example 1, except that a 0.5% solution of a mixture of the cationic polymer of Example A with the anionic polymer of Example F is used, the weight proportion between the cationic polymer and the anionic polymer being 1: 3. The amount of resin deposited on the fibers is 7.2%. The refined paste is mixed with wood pulp and sheets are prepared and evaluated as in Example 8. The resulting sheets have a gloss of 87%, an opacity of 79.3% and a tensile strength of 77 %.

Example 11

The polypropylene of Example 1 is replaced by 90 parts of high density polyethylene (Du Pont, melt flow index 5.5-6.5 at 190 ° C.) and the mixture is sprayed with an ethylene-acid copolymer. acrylic from the solution in methylene chloride at 200 ° C and under 70 kg / cm2 of pressure. The fibrous product is refined on disc as in Example 1, and the refined pulp is mixed with wood pulp and leaves are prepared and evaluated as in Example 8. The resulting leaves have a gloss of 84%, an opacity of 80%, a tensile strength of 68% and a Mullen resistance to bursting of 69%.

Example 12

130 parts of polypropylene with an intrinsic viscosity of 2.2 are used in decahydronaphthalene at 135 ° C., 870 parts of methylene chloride, a temperature of 222 ° C. and a pressure of 70 kg / cm 2 are used in the preparation of a fibrous product, following the process of Example 1. 60 parts of fibrous product are suspended in 6000 parts of water, the suspension is stirred and air containing air is passed through it at room temperature 0.025 g / dm3 of ozone, at a rate of 1.7 dm3 / minutes for a period of 15 minutes. Under these conditions, the absorption of ozone by the fiber is 0.53% of the weight of fibers, and the fibers have an acid number corresponding to 0.033 milliequivalents of carboxyl groups per gram of fiber. The ozonized wet fibers are refined on disc as in Example 1 and it is found that the purified product contains 5.4% of resin fixed according to the nitrogen analysis. The purified paste is then mixed with wood pulp (50:50 RBK: WBK 750 according to the "Canadian Standard Freeness" units), and leaves are prepared and evaluated.

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as in Example 8. The resulting sheets have a gloss of 87.3%, an opacity of 87.6% and a tensile strength of 84%.

Example 13

The process of Example 12 is repeated except that the reaction with ozone is carried out for one hour. Ozone absorption is 1.9% by the fibers, and the fibers have an acid number corresponding to 0.12: 9 milliequivalents of carboxyl groups per gram of fiber. After refining on disc, the fibers contain 5.1% of fixed resin, and the sheets prepared according to Example 8 have a gloss of 87.2%, an opacity of 87.7% and a tensile strength of 89%.

Example 14

The process of Example 13 is repeated, except that high density polyethylene is used instead of polypropylene, and pentane is used as a solvent instead of methylene chloride. The ozone absorption is 1.2%, the acid number is 0.115 milliequivalents per gram, the quantity of fixed resin is 8.8% and the leaves have a gloss of 85%, an opacity of 87% and a tensile strength of 100%.

Example 15

Generally following the technique of Example 12, a fibrous product sprayed by discharge is prepared from high density polyethylene grafted with 5% maleic anhydride, a 1% suspension of 60 parts of fibers is prepared in the water and ozone is passed through the fiber suspension for 1 hour at 25 ° C at a rate of 0.039 g / minute. The ozonized fibers are refined on disc, until reaching a consistency of 0.125% in an aqueous medium containing 0.05% of the resin mixture of Example 1. The absorption of resin in the refining process is 5, 4%, and after mixing with wood pulp and shaping into a sheet as in Example 8, the resulting sheets have a gloss of 87.5%, an opacity of 85% and a tensile strength of 85%.

Example 16

A fibrous polypropylene product is prepared by applying conditions comparable to those given in Example 12. A portion of this product is mixed with 5% by weight, relative to the polypropylene fibers, of wood pulp (50:50 RBK : WBK) and the fibrous mixture is purified until it becomes dispersible in water. A dispersion of 1% of the mixture is then ozonized in water by passing the ozone through the dispersion of fibers at room temperature until the ozonized fibers have an acid number corresponding to 0.07 milliequivalents. of carboxyl groups per gram of fiber. 30 parts of ozonized pulp are mixed with 70 parts of wood pulp and added to portions of the resulting mixture in papermaking vats, 5% relative to the total weight of fibers (a) of the resin mixture of the Example 1, (b) of the mixture of cationic polymer of Example B with the anionic polymer of Example E, the cationic: anionic proportion being by weight of 1: 5, (c) of the mixture of cationic pelymer of Example C with the anionic polymer of Example E, the cationic: anionic proportion being by weight of 1: 5, and (d) of the mixture of cationic polymer of Example D with the anionic polymer of Example E, the cationic: anionic proportion being by weight of 1: 5. After an intimate admixture of the adjuvants with the dough, sheets are prepared and evaluated as described in Example 8. The results are given in Table II.

Table II

Adjuvant

Shine

Opacity

Resistance

tensile

(%)

(%)

(%)

(at)

87.8

84.5

67

(b)

87.1

84.3

68

(vs)

87.6

84.4

74

(d)

87.8

84.2

69

Comparative data from the evaluation of representative prior art processes and polymeric adjuvants are presented in the following examples. All quantities are again based on parts by weight.

Comparative Example 17 Following the procedure of Example 1, a fibrous product was prepared from 95 parts of polypropylene and 5 parts of copolymer of this ethylene-acrylic acid example, and separate portions of the fibrous product were refined into aqueous medium containing 0.1% (a) of a mixture of resin from Example 1, (b) of a 1: 1 mixture of melamine-formaldehyde-polymer (Paramel He, American Cyanamid) and carboxymethyl-cellulose (CMC, DS 0.4 Hercules) and (c) a 2: 1 mixture of Paramel polymer and CMC polymers. Each resulting paste is mixed with wood pulp and leaves are prepared and evaluated, all as described in Example 8. The results are presented in Table III.

Table III

Adjuvant

Shine

Opacity

Resistance

Resistance

tensile

to burst

(%)

(%)

(%)

(%)

(at)

82.5

87.0

73.5

56.0

(b)

81.8

86.7

38.2

24.9

(vs)

84.3

88.2

44.1

26.0

These data show that the replacement of the resin mixture (a) by the known mixtures (b) and (c) in the process according to the present invention does not provide a paper having the desired resistance.

Comparative Example 18 A fibrous product sprayed by discharge, practically identical to that of Example 1, is refined on disc for 6 minutes in water in a Sprout Waldron disc refiner until a consistency of 0.25% is obtained. . The refined pulp is mixed with bleached kraft wood pulp (50:50 RBK: WBK, 500 "Canadian Standard Freeness"), as in Example 8, and in papermaking vats are added to portions of the resulting mixture 5% relative to the total weight of fibers (a) of the resin mixture of example 7 (b) of the mixture of cationic polymer of example B with the anionic polymer of example E, the proportion by weight between the cationic polymer and the anionic polymer being 1: 3, (c) of the mixture of cationic polymer of example C with the anionic polymer of example E, the proportion by weight between the cationic polymer and the anionic polymer being 1 : 3 and (d) of the 2: 1 mixture of Paramel polymer and CMC of Example 17. Additional portions of dough mixture are treated in a similar manner with 1.5% of (a), (b), ( c) and (d), based on the total weight of fibers. Sheets are prepared and evaluated as described in Example 8. The results are given in Table IV.

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Table IV

Adjuvant

Shine

Opacity

Resistance

Resistance

tensile

to burst

(%)

(%)

(%)

(%)

5.0% (a)

82.5

82.4

87

102

5.0% (b)

81.0

83.8

75

103

5.0% (c)

81.3

80.3

92

86

5.0% (d)

85.6

82.0

50

52

1.5% (a)

85.1

83.6

67

69

1.5% (b)

84.6

82.9

70

68

1.5% (c)

84.0

81.6

70

95

1.5% (d)

86.5

83.1

55

40

It appears from the above data that the additives (a), (b) and (c) according to the present invention provide better resistance to paper than the known additive (d).

Comparative Example 19 A fibrous product sprayed by discharge is prepared as in Example 1, except that the ethylene-acrylic acid copolymer is omitted and 100 parts of polypropylene are used. The refining of separate portions of the fibrous product is carried out in a Waring type kneader, in an aqueous medium containing 1.0% (a) of the resin mixture of Example 1, (b) of the 1: 1 mixture of Paramel polymer and of the CMC of Example 17 and (c) of the 2: 1 mixture of the Paramel polymer and of CMC of Example 17. The resulting pulps are mixed with wood pulp and sheets are prepared and evaluated as described in Example 8. Table V presents the results obtained.

Table V

Adjurant

Shine

Opacity

Tensile strength

Burst resistance

(%)

(%)

(%)

(%)

(at)

(b)

(vs)

87.6 89.6 89.2

87.5 87.8 88.2

47.7 36.2 36.9

37.1 22.9 26.3

These data again show the superiority of the additive (a) according to the present invention over the known additives (b) and (c). In addition, by comparison with Example 17, the data concerning the additive (a) show the importance of the carboxylic functions of the anionic polyolefin composition used in accordance with the process of the present invention.

Example 20

80 parts of polypropylene of Example 1 and 20 parts of styrene-maleic anhydride copolymer (ARCO, 75:25 styrene maleic anhydride, molecular weight 19,000) are loaded into a closed autoclave with 250 parts of hexane and 250 parts of water. The contents of the autoclave are stirred and heated to 220 ° C., the vapor pressure in the autoclave then being brought to 70 kg / cm 2 with nitrogen. The resulting emulsion is discharged out of the autoclave into the atmosphere by an orifice 1 mm in diameter and 1 mm in length, giving rise to the formation of a fibrous product.

Parts of the fibrous product are refined on disc for 6 minutes in a Wal-dron Sprout disc refiner to a consistency of 0.25% in (a) water, (b) an aqueous solution at 0.5 % of cationic polymer of Example A, (c) a 0.5% aqueous solution of poly (acrylamide-co-acrylic acid) modified with glyoxal (Parez 631 NC, American Cyanamid), (d) an aqueous solution with 0.5% of melamine-formaldehyde polymer (Paramel He, American Cyanamid), (e) a 0.5% aqueous solution of cationic starch and (f) a 0.5% aqueous solution of a mixture 1: 3 of cationic polymer of Example A and of the anionic polymer of Example F. Each resulting pulp is mixed with wood pulp and leaves are prepared and evaluated, the whole as described in Example 8 The data thus obtained are given in Table VI.

Table VI

Middle of

Shine

Opacity

Resistance

Refining resistance

tensile

to burst

(%)

(%)

(%)

(%)

(at)

84.2

81.3

41

30

(b)

85.2

79.8

51

48

(vs)

85.5

81.4

39

32

(d)

81.6

82.5

48

38

(e)

84.8

79.2

54

48

(f)

82.1

79.4

72

71

These data show that the individual additives used in the process according to the present invention are by no means as effective in ensuring a paper having the appropriate strength, as is a mixture of the specific cationic and anionic polymers according to the present invention, such as mixture used in (f).

The method according to the invention is quite simple and attractive for the reason that it provides synthetic pulps which, when mixed with wood pulp, lead to paper products whose gloss, opacity, Smooth surface and printability are improved at low sheet weight, compared to conventional loaded or unfilled paper. Likewise the fact that synthetic pulps according to the invention do not require the presence of separate water-soluble additives, such as starch, is advantageous in the manufacture of paper, these not being made necessary by the presence of the cationic polymer component incorporated into the modified fibers produced by the process according to the present invention.

In the process according to the invention, the anionic polyolefin composition can be a polyolefin containing carboxyl groups which have been introduced into the polymer molecule by grafting of polyolefin with a monomer containing carboxyl groups or by oxidation of the polyolefin by oxygen or ozone, or the composition may be a polyolefin in admixture with an anionic polymer containing carboxyl groups. In any case, the polyolefin can be polyethylene, polypropylene, an ethylene-propylene copolymer or a mixture of any of these polyolefin materials.

When an anionic polyolefin composition is a mixture of a polyolefin and an anionic polymer containing carboxyl groups, the latter component can be a polyolefin containing carboxyl groups directly attached to the polymer backbone, a polyolefin grafted with the acid acrylic, methacrylic acid, maleic anhydride or mixtures thereof, a copolymer of any of the following: ethylene, propylene, styrene, alpha-methylstyrene, or their mixtures with any of the following: acrylic acid, acid methacrylic, maleic anhydride or mixtures thereof, as well as mixtures of any of these anionic polymer components. Again, when specified, the polyolefin can be polyethylene, polypropylene, an ethylene-propylene copolymer, or mixtures thereof.

In the previous mixtures of polyolefin and anionic polymer containing free or anhydride carboxyl groups, the proportion between the first and the last is preferably from about 95: 5 to about 80:20 by weight, and the amount of carboxyl groups available in the poly-

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anionic mother is preferably about 3 to about 30% by weight. In general, the anionic polyolefin composition used in the process according to the present invention contains a sufficient amount of carboxyl groups to provide at least 0.01, and preferably at least about 0.04 milliequivalents of carboxyl groups per gram of polyolefin paste . In addition, the amount of carboxyl groups is preferably such that it provides up to about one thousand equivalent of carboxyl groups per gram of polyolefin paste. A particularly desirable range is from about 0.04 to about 0.2 milliequivalents per gram.

The dispersing medium used during the fiber formation step in the process according to the invention contains an organic solvent which is a non-solvent at its normal boiling point for the polyolefin composition used to form the fibers. . It can be the methylene chloride indicated in most of the examples or other halogenated hydrocarbons, such as chloroform, carbon tetrachloride, methyl chloride, ethyl chloride, trichlorofluoromethane and l, l, 2 -trichloro-1,2,2-trifluoroethane. Also useful are aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane and their isomers and alicyclic hydrocarbons such as cyclohexane. Mixtures of these solvents can be used and water can be present if desired to form an emulsion of the polyolefin composition. In addition, the pressure generated by the solvent vapors can be increased, and normally it is, by an inert pressurized gas such as nitrogen or carbon dioxide.

When the fiber forming process is carried out, the concentration of the polyolefin composition in the solvent solution normally ranges from about 5 to about 40% by weight, preferably from about 10 to about 20% by weight. weight. The temperature at which the dispersion of the polyolefin composition in the solvent is heated to form a solution of the composition depends on the particular solvent used and must be high enough to effect the dissolution of the composition. The fiber forming temperature is generally about 100 to about 225 ° C. The pressure on the solution of the polyolefin composition can be from about 42 to about 105 kg / cm2, but it is preferably between about 63 and about 84 kg / cm2. The orifice through which the solution is discharged may have a diameter of about 0.5 to about 15 mm, preferably about 1 to 5 mm and the proportion between the length of the orifice and its diameter should be about 0.2 to about 10.

During the fiber modification step, the fibers of the fibrous anionic polyolefin composition are intimately mixed with a dilute aqueous solution or dispersion of a mixture of the cationic and anionic polymers containing nitrogen which have been specified. The proportion between the cationic and anionic polymer in the mixture ranges from 1: 3 to 1: 7 by weight. The cationic polymer component in the above mixture can be generally classified as a reaction product of epichlorohydrin and a polymer containing secondary or tertiary amine groups or both. A representative group of polymers belonging to this defined class can for example be the cationic polymer component used in many examples, namely, the reaction product of epichlorohydrin and amino polyamide from diethylenetriamine and adipic acid. The preparation of this product is presented in Example A. However, more generally this group of cationic polymers comprises the reaction products of epichlorohydrin and an amino-polyamide originating from a dicarboxylic acid and from polyalkylene polyamine having two primary amine groups and at least one secondary or tertiary amine group,

all as described by US Patents 2,926,116 and 2,926,154.

Another representative group of polymers belonging to the broadly defined class of cationic polymers is that in which the polymers are water-soluble reaction products of epichlorohydrin and a polyalkylene polyamine. The preparation of an example product from this group is presented in Example B.

The polyalkylene polyamines which are reacted with epichlorohydrin have the formula H2N (CnH2nNH) xH where n is an integer from 2 to 8 and x is an integer equal to 2 or more, preferably from 2 to 6 Examples of these polyalkylene polyamines are polyethylene polyamines, polypropylene polyamines and polybutylene polyamines. Specific examples of these polyalkylene polyamines include diethylene triamine, triethylene tetramine, tetraethylene pentamine, bis (hexamethylene) triamine and dipropylene triamine. Other polyalkylene polyamines which can be used include methyl-bis (3-amino-propyl) -amine, methyl-bis (2-aminoethyl) -amine and 4,7-dimethyl-triethylene-tetramine. Mixtures of polyalkylene polyamines can also be used if desired.

The relative proportions of polyalkylene polyamines and epichlorohydrin can be varied depending on the particular polyalkylene polyamine used.

In general, it is preferred that the molar proportion between the epichlorohydrin and the polyalkylene polyamine is greater than 1: 1 and less than 4.5: 1. When preparing the water-soluble resin from epichlorohydrin and tetraethylene pentamine, good results are obtained with molar proportions of about 1.4: 1 to 1.94: 1. The reaction temperature is preferably about 40 to about 60 ° C.

Another group of cationic polymers useful according to the present invention is that in which the polymers are reaction products of epichlorohydrin and a poly (diallyl-amine). The preparation of a product of this kind is presented in Example C. Additional products and the process for preparing them are presented in US Pat. No. 3,700,623.

The final group of cationic polymers used according to the present invention is that in which the polymers are the reaction products of epichlorohydrin and a polyaminourylene. The preparation of one of these products is given in Example D. Related products and their preparation are described in US Patent No. 3,240,664.

The anionic polymer component of the aqueous solution or dispersion in which the fibers of the anionic polyolefin composition are modified is illustrated in the examples. One of these is the reaction product of glyoxal and the Polyacrylamide obtained by copolymerization of acrylamide and acrylic acid. The preparation of an example product is presented in Example E. The amount of acrylic acid units in the copolymer is from 2 to 15%. Comparable products can be prepared by partial hydrolysis of polyacrylamide or poly (acrylamide-alkyl co-acrylate) such as a copolymer of acrylamide with ethyl acrylate. Any of these polyacrylamides can be prepared by conventional methods for the polymerization of water soluble monomers and they preferably have molecular weights of less than about 25,000, for example in the range of about 10,000 to about 20,000.

The other anionic polymer, containing nitrogen, presented in the examples is the reaction product of glyoxal and of the polymer obtained by partial hydrolysis of branched, water-soluble poly (beta-alanine). The preparation of a representative product is indicated in Example F. The poly (beta-alanine) can be prepared by anionic polymerization of acrylamide in the presence of a basic catalyst such as sodium hydroxide, and a vinyl or radical polymerization inhibitor

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free, such as phenyl-beta-naphthylamine, and the polymer has a molecular weight of about 500 to about 10,000, preferably about 2000 to about 6000. Due to the extremely exothermic nature of anionic polymerization, it it is preferable to conduct the reaction in an appropriate organic reaction medium, such as toluene or chlorben-zene, inert under the conditions of the reaction and capable of dissolving or allowing the suspension of the acrylamide.

The branched poly (beta-alanine) produced as described above is a neutral polymer and requires anionic modification for the purpose of the present invention. The anionic modification of branched poly (beta-alanine) is carried out by partial hydrolysis of the polymer to transform a number of primary amide groups into anionic carboxyl groups. For example hydrolysis of poly (beta-alanine)

can be done 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 1 to 10 mol%, and preferably from about 2 to about 5 mol%, based on the recurring amide units.

Each of the anionic nitrogen containing polymers described above is modified by glyoxal to provide the desired anionic, water soluble, nitrogen containing polymers used in accordance with the present invention. The reaction with glyoxal can be carried out in a dilute neutral or weakly alkaline aqueous solution of the polymer, at a temperature of about 10 to about 50 ° C, preferably about 20 to

about 30 ° C. The amount of glyoxal used in the reaction mixture can be from about 10 to about 100 mol%, preferably from about 20 to about 30 mol%, based on the recurring amide units in the polymer. The resulting solutions have good stability.

The process according to the invention makes it possible to prepare improved paper products from a mixture of wood pulp and polyolefin pulps. The process is based on the particular combination of cationic and anionic, nitrogen-containing polymers used during the fiber modification step, and this preferably involves the use of a refining process such as disk refining. In addition, the process depends on various critical factors, namely the presence of at least 80% polyolefin in the mixture of polyolefin is anionic polymer containing carboxyl groups, when the mixture constitutes the anionic polyolefin composition containing a carboxylic functionality. used as a fiber-forming material, an intrinsic viscosity of at least 1.0 for the polyolefin, carboxyl groups available in sufficient quantity in the anionic polyolefin composition containing a carboxylic functionality and a sufficient quantity of resin in the solution or the aqueous dispersion, in which the anionic fibers are modified. However, operation within the limits of these conditions makes it possible to produce a synthetic pulp which, mixed with wood pulp, provides a paper product having a tensile strength of at least 70% of that 100% wood pulp, as well as improved gloss, opacity and smooth surface.

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Claims (12)

618,474 2 1. A process for the preparation of hydrophilic polyolefin fibers, characterized in that it comprises the production of an intimate mixture of a fibrous polyolefin composition obtained by spray projection, containing free carboxyl groups or in the form of anhydride, with a dilute aqueous mixture of anionic and cationic polymers, containing nitrogen, water-soluble, the cationic polymer being the reaction product of epichlorohydrin and (a) of an amino-polyamide originating from a dicarboxylic acid and a polyalkylene polyamine having two primary amino groups and at least one secondary or tertiary amine group, or (b) a polyalkylene polyamine having the formula H2N (CnH2nNH) xH, where n is an integer from 2 to 8 and x is an integer of 2 or more, or (c) a polydial-lylamine or (d) a poly-amino-urylene from urea and a polyamine having at least three amino groups , at least one of which is tertiary, and the anionic polymer eu being the product of the reaction of glyoxal and (a) of a polyacrylamide containing from 2 to 15% of acrylic acid units or (b) of branched poly (beta-alanine), partially hydrolyzed, containing from 1 to 10 mol% of carboxyl groups with respect to the recurring amide units, the proportion by weight between the cationic polymer and the anionic polymer being from 1: 3 to 1: 7. 2. Method according to claim 1, characterized in that the fibrous polyolefin composition obtained by spray projection is based on polyethylene or polypropylene. 3. Method according to claim 2, characterized in that the composition of fibrous polyolefin was obtained by spraying discharge discharge of a mixture of polypropylene and an anionic polymer containing free carboxyl groups or in the form of anhydrides. 4. Pr cede according to claim 3, characterized in that the polymer; he anionic is a copolymer of ethylene and acrylic acid. 5. Method according to claim 2, characterized in that the fibrous polyolefin composition is prepared by spraying polypropylene and oxidizing the resulting fibers to introduce carboxyl groups into the polypropylene molecule. 6. Method according to one of claims 1 to 5, characterized in that the cationic, water-soluble, nitrogen-containing polymer is the product of the reaction of epichlorohydrin and an amino polyamide originating from an acid dicarboxylic and polyalkylene polyamine having two primary amino groups and at least one secondary or tertiary amine group. 7. Method according to claim 6, characterized in that the amino-polyamide comes from adipic acid and diethyl-netriamine. 8. Method according to one of claims 1 to 7, characterized in that the anionic, water-soluble, nitrogen-containing polymer is the reaction product of glyoxal and of the polyacrylamide obtained by copolymerization of acrylamide with acrylic acid. 9. Method according to one of claims 1 to 7, characterized in that the anionic, water-soluble, nitrogen-containing polymer is the reaction product of glyoxal and of the polymer obtained by partial hydrolysis of a poly (beta-alanine ) branched water-soluble. 10. Hydrophilic polyolefin fibers obtained by the process according to claim 1. 11. Use of the hydrophilic polyolefin fibers according to claim 10 for the manufacture of paper. 12. Mixture of water-soluble cationic and anionic polymers containing nitrogen for carrying out the process according to claim 1, characterized in that the cationic polymer is the reaction product of epichlorohydrin and aminopolyamide originating from adipic acid and diethylene triamine and in that the anionic polymer is the reaction product of glyoxal and polyacrylamide obtained by copolymerization of acrylamide and acrylic acid.