DE3929108A1 - Wet strength paper is prepd. - Google Patents

Abstract

Wet strength paper is prepd. by (1) addn. to cellulose suspension of polyaminopolyamide-epichlorohydrin resin (I) and, as polymerisation accelerator, reaction prod. (II) of carboxymethylcellulose or its Na salt, having degree of substn. at carboxmethyl gps. 0.25-0.70 and contg. 20-40 wt.% basic substance, with epichlorohydrin, in molar ratio 1.0:0.02-0.04 (2) forming cast paper prod from mixt. (3) drying and pressing. 0.1-1.5% (II) on absolutely dry wt. of cellulose in suspension is used. Fillers and functional additives are also added to cellulose suspension.

Description

 The present invention relates to extraction of substances that harden the thermosetting Synthetic resins accelerate in the manufacture of cellulose-containing wet strength materials are used, and in particular it relates to a polymerization accelerator for wet strength resins and a process for their production of wet strength paper.

The proposed invention is used in pulp and paper industry and in the textile industry use Find.

One of the current problems in the pulp and paper industry consists of mechanical solidification of paper and cardboard when wet. This is required to the increased tearing off of a paper web both in the course of their formation, as well as in a further use by the To prevent consumers. For wet consolidation purposes serve substances of different chemical nature, whereby the selection of the same according to the type of to be produced Production aimed. Any of these substances enables the execution of the process in acid, neutral or alkaline medium. The world practice of the last Years clearly shows a tendency to technological processes in a medium close to neutral. This is on the pursuit of reducing the amount of addable  Chemicals, expanding the range of applicable Fillers, extending the life of the manufactured products and on the specifics of Technology attributed to their continued use.

When producing wet strength paper in a neutral Medium is largely used polyamine polyamide epichlorohydrin resins. The following circumstances contribute to this their high effectiveness, unlimited solubility in water, their strong flocculation ability and the lack of free Formaldehyde. Like all other resins in the field come into use, but have the above Resins a significant disadvantage, i. H. a slow one Hardening in finished production (paper and cardboard). Thereby the final value of wet strength is not at the moment the production but after the expiration of a certain Period of time, which is often very long.

A method for producing wet strength paper is known (US, A, 30 58 873), which the addition of 0.5 up to 2% by mass of polyamine polyamide epichlorohydrin resin and 0.1 up to 0.2 mass% polymerization accelerator to the pulp slurry provides for a concentration of 2.5% and freeness are 750 units, being the polymerization accelerator Carboxymethyl cellulose (KMZ), a technical product from Herkules (US), carboxymethyl cellulose is characterized by a 0.7 Degree of substitution on carboxymethyl groups and a basic substance content from 80%.

The scraps of paper obtained turn into handmade samples formed by pressing and then drying. The Wet strength value of paper, i. H. the breaking load when wet, increasing from 4.8 to 7.8 to 5.8 up to 9.1 pounds / inch (depending on resin expenditure). To Increase this value to 7.9 to 13.5 pounds / inch an additional heat treatment at a temperature of 105 ° C expedient to carry out within 60 min.  

The results mentioned show that the maximum effect using the accelerator together (Carboxymethyl cellulose) with implementation of the additional Heat treatment can be achieved: the however, the latter step is very expensive, which makes the Benefit of the known method is reduced. The carboxymethyl cellulose as described in the patent also contains 80% basic substance, what only in the case of washing carboxymethyl cellulose by-products from the reaction is achieved. The yield of finished Product by esterification of pulp according to the calculations should not exceed 40%. And in the end the known method is relatively ineffective, because the increase in wet strength is only 16 to 21% can be observed. Since the process on the manufacture Aiming of ash-free paper, the effect achieved be even lower with a filler application.

The invention has for its object a polymerization accelerator for wet strength resins by modification of carboxymethyl cellulose and a process for the production of wet strength paper using this Develop accelerator, the higher one Wet strength value of the paper with various Ash content without additional energy and material would secure.

The object is achieved in that a polymerization accelerator is proposed for wet strength resins, which is a product of the implementation of carboxymethyl cellulose or their sodium salt, the one between 0.25 and 0.70 degree of substitution on carboxymethyl groups has and contains 20 to 40% by mass of basic substance, with epichlorohydrin at a molar ratio of 1.0: 0.02 to 1.0: 0.04.

The accelerator according to the invention contains such chemically active epoxy fragments, which are more reluctant of wet strength resin and creating cheap ones  Resin hardening conditions during storage of the cellulosic materials produced cause. The accelerator with this composition results an increase in the wet strength value at the moment of Production by about 50% and contributes to the increase in speed and size of this characteristic value for storage of cellulose-containing materials. The polymerization accelerator works with wet strength resins in an PH range from 4 to 9 during manufacture of paper with different ash content.

A method for producing is proposed Wet strength paper by adding a polyamine polyamide epichlorohydrin resin and a polymerization accelerator for Cellulose slurry, formation of a hand scoop pattern the mass obtained with subsequent pressing and drying the same in the present invention as a polymerization accelerator a product created by Conversion of carboxymethyl cellulose or its sodium salt, which have a degree of substitution between 0.25 and 0.70 of carboxymethyl groups and 20 to 40% by mass Contains basic substance, with epichlorohydrin at one Molar ratio of 1.0: 0.02 to 1.0: 0.04.

The method according to the invention ensures the increase the wet strength of paper without enlarging the Energy and material expenditure, d. H. without the use of expensive and complicated equipment.

To achieve the optimal wet strength value the said accelerator in an amount of 0.1 to 1.5%, based on the weight of the absolutely dry cellulose, expediently add to the pulp slurry. To expand the range of wet strength paper, are pulp fillers and functional Add additives. The polymerization accelerator according to the invention is by reacting carboxymethyl cellulose (KMZ) or their sodium salt, the one between 0.25 and 0.70 degree of substitution on carboxymethyl groups  has and contains 20 to 40% by mass of basic substance, with epichlorohydrin at a molar ratio of the components from 1.0: 0.02 to 1.0: 0.04. In the Synthesis can commercial carboxymethyl cellulose can be used with the specified parameters or on The consumer's wish can be the synthesis with the manufacture the carboxymethyl cellulose by the known method can be combined, with cotton cellulose as the raw material or halocellulose. Man treats them with an aqueous solution of Alkali metal hydroxide, preferably sodium hydroxide the reactivity through formation of baking soda or To increase hydrate cellulose. Then you give an esterifying agent Monochloroacetic acid or its salt, too, mixed intimate and adds epichlorohydrin. The simultaneous encore with constant stirring of both substances is also allowed. So that the side reaction depth (Hydrolysis of sodium cellulose and sodium monochloroacetate or saponification of the monochloroacetic acid is reduced 17% alkali for mercerization commonly used, and the overall process of adding alkali from and 2 hours after adding epichlorohydrin takes place at a temperature of 12 to 20 ° C. In this temperature range the esterification and Cross-linking reactions. To end these reactions you increase the temperature to values that are different from the Depending on the nature of the esterification agent that can be used.

For dehumidifying the manufactured accelerator and Prevent its hydrolytic cleavage during storage or promotion becomes the latter dried.

The end product is a scatterable substance that is under Loss of fiber structure practically completely soluble in water is. He is used in the manufacture of wet strength pulp uses and serves to increase the effect of wet strength resins, which have mechanical strength ensure these materials are moist and dry.  The mechanism of action of the final product is attributed to the fact that it was added to the pulp is adsorbed on the pulp fiber, increasing the number of functional ones to be interacted with resin Groups are growing and a branched network is formed, which prevents water from entering the cellulose molecule prevented.

From that described in US, A 30 58 873 Substance with the same purpose (technical Carboxymethyl cellulose from Herkules US, whose Degree of substitution on carboxymethyl groups 0.7 and Basic substance content is 80%) Accelerator according to the invention through a further area degrees of substitution and by modifying epichlorohydrin and a lower basic substance content having.

All of the differences mentioned allow the increase in the effectiveness of the invention Accelerator, i. H. his ability to do otherwise the same Conditions to increase the wet strength of the paper. This can be explained in the following way.

The presence of carboxymethyl groups in the stock of the accelerator adsorbed on the cellulose fiber The pulp offers the option of being more effective To interact with the resin because the specified groups against the hydroxyl groups of Cellulose are chemically more active. From this point of view seen from is a degree of esterification of 0.25 to 0.70 (preferably 0.5) optimal. When lowering the lower The limit can be the number of additional active Groupings prove insufficient, and the increase The upper limit can be used when drying paper lead to thermo-oxidative hydrolytic degradation, which the Effectiveness of the accelerator according to the invention is reduced.

The reduction in the degree of substitution of carboxymethyl groups also causes a reduction in ver  consumption of ester medium, which gives the additional advantages attributed to the accelerator according to the invention is.

The addition of epichlorohydrin activates the accelerator probably because of its interaction is facilitated with the resin because of this interaction not difficult to access for steric reasons Hydroxyl groups but the more easily accessible and perhaps chemically more active epoxy fragment is involved. The optimal epichlorohydrin consumption starting from 0.02 up to 0.04 mol per 1 mol carboxymethyl cellulose or sodium salt the same is due to the need for one to secure a sufficient number of polymerization nuclei, and on the other hand by preventing such a degree of networking of the macromolecule of carboxymethyl cellulose, where the accelerator loses its water solubility.

Both accelerators, i. H. the invention and that described in US, A 30 58 873, are characterized by the term "basic substance". There in the synthesis of cellulose esters and products based on a whole series of side reactions, namely Hydrolysis of sodium cellulose, saponification or hydrolysis of the esterification agent, hydrolysis of the crosslinking agent, in particular of epichlorohydrin, runs the response is a complicated system in which the ester content described with the term mentioned above and quantitative analysis of precipitation in the form of copper salt is determined.

According to the amount of the main component of carboxymethyl cellulose Herkules US, which is 80%, to close, the KMZ is prepared by washing. in the The difference to this is washing in the synthesis of the accelerator according to the invention excluded, whereby it contains 20 to 40% basic substance, of which at by-products of the reaction, the sodium glycolate (35 to 40%) dominates, which is due to saponification  (Hydrolysis) of the esterification agent. As the carboxy group-containing substance is capable of Hardening resins that catalyze the epoxy group contain. The exclusion of the washing process from the Technology for the production of the accelerator therefore makes the technology not only more economical but also allows against the effectiveness of the accelerator the accelerator from Herkules US.

The process of making wet strength paper is carried out according to the invention as follows. You prepare a slurry of three types of pulp, namely bleached refined sulphate pulp from softwood (20% by mass), Mixed wood pulp (30% by mass) and hardwood pulp (50% by mass). Because the hardwood pulp has the strength properties materially reduced, its use in the pulp was dictated by the desire the accelerator according to the invention under hard Check conditions. For paper production the Pulp from two first grades in a centrifugal grinder according to the standard procedure until achieved a freeness of 30 ° SR and the hardwood pulp dissolved in a pulper. After determining the concentration will the required mix composed. Then you set the polymerization accelerator, a slurried filler (of various types) Natural) and a polyamine polyamide epichlorohydrin resin "Nadavin LT" too by looking at the components of the series as stated above after stirring the Add mass with each of the ingredients. The paper pulp composition is the following: up to 100 mass% fiber, 11 to 24.9 mass% filler, 0.3 to 0.4 mass% Resin, 0.1 to 1.5 mass% accelerator.

Fillers usually become an extension of the pulp of the range and production of special paper (for example decorative paper) added. If missing Fillers and functional additives, d. H. in the preparation of however, the accelerator shows ashless paper a higher effectiveness.  

The accelerator can be the pulp slurry added at a temperature reduced to 15 ° C. and it also increases the wet strength value. This will give the opportunity to differentiate the process Using climatic conditions has expanded. The Accelerator is when using resins of other types (Luresin, Kümene) and other chemical nature (for example Melamine-formaldehyde resins) sufficiently effective. He It also does not lose its viscosity increasing activity of the resin to 0.15 Pa · s, as it ages the case is.

Laboratory samples of wet-strength paper weighing 3.90 ± 0.15 g To prepare, hand-made samples are made from the Paper pulp shaped and on a sheet of paper then pressed and dried. Half of the manufactured Samples are subjected to additional heat treatment a temperature of 110 ° C within 5 min.

For all samples produced one determines according to the known methods of breaking strength in dry and wet Condition, the proportion of ash mass and the reluctance of the filler. When determining the breaking strength for paper when wet, the time is where the samples get wet, 30 s.

Below are the concrete embodiments of the proposed invention.  

example 1

It is poured into a jacketed reactor 140 l of water and gives 120 kg of commercially available sodium salt the carboxymethyl cellulose at a temperature of 16 ° C with continuous stirring within 1 hour to, the carboxymethyl cellulose being 0.5 Has degree of substitution on carboxymethyl groups and contains 30% by mass of basic substance. You bet afterwards 0.826 kg epichlorohydrin at a molar ratio to Carboxymethyl cellulose such as 0.04: 1, stirs within 1 hour and then holds the reaction mass within 2 hours at a temperature of 65 ° C. The produced polymerization accelerator becomes Dehumidify dried at 100 ° C.

Example 2

In a jacketed reactor, a 17% Sodium hydroxide solution pumped in, the temperature the same is kept between 12 and 30 ° C. In the alkali solution bring 35 kg of pulp (based on the absolutely dry substance) with continuous stirring and performs the mercerization within 1.5 hours by. The monochloroacetic acid is added to the hydrate cellulose or their sodium salt as an esterifying agent and keep the mixture at the specified temperature within 1.5 hours. Then a required one Amount of epichlorohydrin in a molar ratio to Carboxymethyl cellulose such as 0.02: 1 to 0.04: 1 added, continuing stirring within 2 hours, the temperature increased to 60 to 90 ° C and the mixture maintains at this temperature within 2 hours. To the termination of the esterification and crosslinking reaction the product is made to dehumidify at 100 ° C dried. Table 1 below gives the technological Parameters different embodiments  of the described process and characteristic values of the manufactured Polymerization accelerator.

Table 1

Embodiments of Example 2

Continuation of table 1

Example 3

38.4 g bleached refined sulfate pulp on softwood and 57.6 g mixed wood pulp are placed in a centrifugal grinder until a grinding degree of 26 ° SR ground together; 96.0 g of hardwood pulp dissolved in a pulper (the pulp is covered indicated on the absolutely dry fiber). The manufactured one Pulp slurry is mixed up with water Diluted 3% and stirred thoroughly. The polymerization accelerator is then set (in fixed or previously solved Condition), the filler suspension with a concentration of 200 g / l and a solution of polyamine polyamide epichlorohydrin resin Variety "Nadavin LT" with a concentration of 20 g / l, taking the components in order as stated above after thoroughly stirring the mass with each who admits components. The composition of the pulp (as stated above) is as follows: up to 100% by mass Fiber, 11 to 24.9% by mass filler, resin and accelerator amount fluctuates in a range from 0.3 to 0.4 mass% or 0.1 to 1.5 mass%, the filler is also used of different nature.  

The paper pulp produced becomes 3.90 ± 0.15 g heavy laboratory samples made from wet strength paper. The prepared mass is diluted 10 times with water.

Cast products are formed by means of a sheet apparatus, which are then pressed and dried.

Half of the samples produced are subjected the additional heat treatment at a temperature of 110 ° C within 5 min. For all samples produced one determines the breaking strength according to the known methods in a dry and moist state, (the time when the Samples get wet, 30 s), the ash mass fraction and the reluctance of the filler.

The tablet 2 gives the data of the different embodiments the technological process of manufacture of wet strength paper and its quality indicators.

Table 2

Continuation of table 2

Continuation of table 2

Continuation of table 2

Continuation of table 2

The analysis of the information given shows the following.

The polymerization accelerator according to the invention is not only in filler-free papers, but also in filler-containing papers very effective. Although the encore the filler in the paper composition the mechanical Significantly reduced paper strength (see Embodiments 23 and 13 of Table 2) remains Efficiency of the accelerator sufficiently large. The invention Process can therefore be used to manufacture filler-containing wet-strength papers and not only for production of filler-containing papers, as is known from the  in US, A 30 58 873 Solution the case is used. This method allows the additional heat treatment to be completely excluded, where the wet strength value is equal to or even larger than paper after heat treatment without Accelerator (see embodiments 2 and 3 compared with the embodiment 27 of Table 2) is obtained. The specified result can be obtained if the Acceleration consumption between 0.5 and 1.5%, related on the mass of the absolutely dry pulp, and the amount of resin remains constant. If the accelerator consumption is reduced to 0.1 to 0.5% by mass, then sufficient the short-term (1 day) maintenance of the finished production Room temperature and not at elevated (up to 105 ° C) Temperatures like this after the baknnten in the US, A 30 58 873 solution described takes place, out to a significant increase in the effectiveness of the accelerator to reach. In the area of the tested accelerator quantities (0.1 to 1.5 mass%) occurs the monotonous Growth in wet strength of paper, that of technological Difficulties are not accompanied on. But Consumption exceeding 1.5% by mass is economically inappropriate. These values can also be exceeded affect the color of the paper a little if the Filler also as a pigment (e.g. iron oxide red or iron oxide yellow) serves at the same time.

The test results also show that the accelerator according to the invention in addition to its main purpose, to activate the action of wet strength resins, a Has a number of additional advantages.

First, it does not increase mechanical strength only in a moist but also in a dry state.

Second, when using the accelerator the reluctance of the filler significantly (from about 72 up to 82%) too, which increases the ash content of paper enabled without additional expenses, d. H. to Filler saving leads.

Third, the accelerator allows difficulties  to avoid which with the decrease in temperature of the ambient air and the process water in winter are connected. As already pointed out, the Mechanism of action of the wet strength resin after its adsorption on the pulp. With the decrease in temperature the capacity of sorbents decreases, and this inevitably brings about a reduction in the wet strength. The wet strength remains in the presence of the accelerator of the paper practically unchanged if the Sheet formation temperature from 20 to 12 ° C (Examples 5, 7 of table 2) decreases. Maybe that’s to explain that the polymerization accelerator by clicking on the cellulose is sorbed, additional polymerization nuclei for resin and that restores the Sorption capacity favored.

Fourth, when using the accelerator an epichlorohydrin-containing paper for the production of the wet-strength paper Resin with a significantly higher viscosity use what happens when the storage guarantee expires. If the accelerator is missing, the viscosity increases for a strong drop in wet strength (embodiments 26 and 27 of Table 2) while in the presence of the same (Embodiments 6 and 5) does not occur.

Table 3 below gives comparatively that Effectiveness of the accelerator, d. H. carboxymethyl cellulose the company Herkules, US and the invention Accelerator. For the purpose of obtaining comparative information are Table 2 embodiments 13 and 14 taken for filler-free papers.

Table 3

The information in Table 3 shows that the invention Accelerator in the manufacture of carefree (ashless) paper one by a factor of 1.5 to 3 higher effectiveness compared to the accelerator Hercules company.

Claims (4)

1. Polymerization accelerator for wet strength resins, which a product of the implementation of carboxymethyl cellulose or of their sodium salt, which are between 0.25 and 0.70 Has degree of substitution on carboxymethyl groups and Contains 20 to 40% by mass of basic substance, with epichlorohydrin at a molar ratio of 1.0: 0.02 to 1.0: 0.04. 2. Method for producing wet strength paper by adding a polyamine polyamide epichlorohydrin resin and a polymerization accelerator for pulp slurry, molding a sample from the obtained mass below then pressing and drying the same, thereby characterized in that as a polymerization accelerator an accelerator according to claim 1 is used. 3. The method according to claim 2, characterized in that said polymerization accelerator in an amount of 0.1 to 1.5%, based on the mass the absolutely dry pulp, the pulp slurry is added. 4. The method according to claim 2, characterized in that the pulp slurry additionally Fillers and functional additives are added.