NZ231637A - Avoiding pitch troubles in pulp manufacture by addition of an acylglycerol lipase - Google Patents

Abstract

A process for preparing mechanical pulp and/or paper containing the mechanical pulp is described, wherein an acylglycerol lipase is used. The process according to the invention avoids the problems caused by the resins in the preparation of mechanical pulp and/or paper containing said pulp.

Description

New Zealand Paient Spedficaiion for Paient Number £31 637 o NO DRAWINGS Priority Date(s): .. A^.\ ' CompleteSpecification Filed: Class: £5i Publication Date: ^ P.O. Journal. No: 231637 No.: Date: NEW ZEALAND PATENTS ACT, 19S3 I on I COMPLETE SPECIFICATION METHOD FOR AVOIDING PITCH TROUBLES rOr DfWc, JUJO PAPER CO., LTD, a Japanese company of 4-1, Oji 1-chome, Kita-ku, Tokyo, Japan, hereby declare the invention for which XL / we pray that a patent may be granted to Hife /us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by page -la-) 231637 TITLE OP'THE INVENTION Method for avoiding pitch troubles BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for avoiding pitch troubles in a process for the production of mechanical pulp and/or of mechanical pulp—containing paper. 2. Prior Art Mechanical pulp, such as groundwood pulp (hereinafter refered to as GP), Refiner groundwood pulp and thermomechanical pulp are produced by a simplified mechanical treatment of grinding logs or. chips by means of a grinder or refiner. The mechanical pulp, which has a defect of providing lower strength, exhibits advantages of providing higher yield, lower costs and higher opacity,* compared with a chemical pulp produced by various chemicals such as alkaline chemicals. On the contrary, the wood constituents remain unchanged in the mechanical pulp.

In general, a wood contains circa 1-10% of pitch, organic solvent—soluble extractive, besides three — la- 231 6 37 major constituents composed of cellulose, hemicellulose and lignin. The amount and quality of pitch vary with wood species. However, it is well-known that softwood, i.e. a main raw material of mechanical pulp, contains a large amount of pitch constituents such as fatty acids, resin acids^-glycerides, etc. In the pulping process, these pitch-constituents are released from pulp, wherein they exist in state of liberation, deposition on fiber surface, and covering thereon. That is, they transform from a fixed state to a liberated state. Pitches suspended in reused water (white-water) are microparticles of about 0.2-2p, which are known as the so-called "colloidal pitch".

In general, a paper is manufactured as follows: Pulps are prepared in various pulping r processes, are treated in a screening process, are mixed with different auxiliaries to prepare a paper furnish. A paper is made from the paper furnish on a paper machine. In a series of processes, the liberated pitch or the deposited pitch is accumulated in pipes, tanks, wire part, or press part, thereby causing the so-called pitch troubles, such as paper contaminations or paper brokes. In the production of a paper containing a large amount of mechanical pulp, pitch troubles occur frequently. As one of the conventional methods for avoiding pitch troubles, there is the so-called seasoning, in which logs after felling are held outside and seasoned in a long period. As another method therefor, there is an addition of surface-active agent in a pulping or paper-making process, as demonstrated in Japanese Patent Publication No.50-22606, wherein the surface active agent includes, for.example, alkylether of polyoxyethylene with various addition moles, alkyl phenyl derivatives, chemicals containing them as a main ingredient.

Although the above seasoning method causes the change and the decrease of pitch constituents in wood mainly by air-oxidation, it requires a broad area and a long period, for example, 3-6 monthes, or more. Accordingly, it is practically difficult to avoid the pitch troubles only by the above seasoning method.

On the other hand, the addition of surface active agent, which is said to disperse the pitch particles and to prevent the pitch deposits, is not $ recognized as a substantial method for avoiding pitch troubles.

SUMMARY OF THE INVENTION It is the object of the present invention to avoid pitch troubles in a process for the production of mechanical pulp or of mechanical pulp—containing paper. The above- object is achieved by treating a paper—stock and/or white-water with an acylglycerol lipase in a process for the production of mechanical pulp and/or of mechanical pulp-containing paper. The object and features of the present invention will become more apparent from the following description.

DETAILED DESCRIPTION OF THE INVENTION In order to obtain an effective method for avoiding pitch toubles, the inventors have investigated in detail: (1) pitch constituents extracted from Japanese red pine (Pinus densiflora) as a typical pulpwood of mechanical pulp and (2) pitch constituents deposited in a process for the production of Japanese red pine-GP and/or of paper containing the pine-GP. As a result, it has been found that the main constituents of the deposited pitch are the same as those contained . ' (/* m 231637 in the original wood and consist mainly of O triglycerides, fatty acids, resin acids and metal salts thereof. Further, it has been demonstrated that the deposited pitch contains always a large amount of triglycerides. It has been assumed that the triglyceride is responsible for one of the main constituents causing pitch troubles. From a point of view that the decomposition or removal of triglycerides by some method is effective for avoiding the pitch troubles, the inventors have investigated various chemical or biochemical methods.

As a result, the object of the present invention has been performed by using an acylglycerol lipase, wherein the triglyceride is decomposed and thus the pitch deposits do not occur without giving harm effects on the pulp or paper qualities and on the run-conditions. That is, the object of the present invention is performed by treating the paper-stock and/or reused water with an acylglycerol lipase.in a process for the production of mechanical pulp and/or of mechanical pulp-containing paper. It is preferred that the acylglycerol lipase is that produced from at least one microorganism selected from the group consisting of 23 1 6 3 7 Aspergillus niger, Pseudomonas fluorescent, Pseudomonas fragi, Geotrichum candidum, and Candida cylindracea The acylglycerol lipase of the present invention is an enzyme for hydrolyzing triglycerides, i.e. one of the main constituents of pitch, wherein any -enzyme, if it hydrolyzes triglycerides, can be used.

Microorganisms for producing the enzyme of the present invention include, for example, Aspergillus niger, Pseudomonas fluorescens, Pseudomonas fragi, Geotrichum candidum, Candida cylindricea, Mucor javanicus, Rhizopus javanicus, Rhizopus delemar, Rhizopus niveus, fungi of genus Rhizopus and the like.

I Among these fungi, Aspergillus niger, Pseucomonas fluorescens, Pseudomonas fragi, Geotrichum candidum and Candida cylindracea are more effective.

The purer the acylglycerol lipase produced from the above microorganisms, the better the effect. Further, the acylglycerol lipases are used alone or in combination. And the good effect can be obtained, too, when the acylglycerol lipase of the present invention is used in combination with other decomposition-enzymes, such as cellulase, hemicellulase, pectinase, protease, etc.

In a process for production of mechanical pulp and/or of mechanical pulp-containing paper, the acylglycerol lipase of the present invention is added to a paper-stock slurry, under agitation or standing. In this case, the enzyme of the present invention is added thereto in an amount of 0.1—10000 ppm (by weight), based on the weight of mechanical pulp, the temperature is preferably 10-70°C, more preferably 35-55°C. At less than 10°C, the enzyme functionates weakly and slowly. At more than 70°C, the enzyme may become inactive. With the increased amount of the enzyme, the reaction is usually accelerated, wherein 10000 ppm of the enzyme, based on the weight of mechanical pulp, is satisfactory, in the calculation from the amount of triglyceride as a substrate. The addition of more than 10000 ppm of the enzyme is economically disadvantageous. The suitable pH—value is 3—1*1, and outside this range,, the activity of the enzyme is decreased reasonably.

In a pulping or paper—making process, there is used a large amount of water of which the major portion is recycled and reused. Since the reused water (white water) contains the pitch constituents, the addition of 23H37 the acylglycerol lipase to white water prevents pitch troubles.

In this case, the superior effects are obtained by the direct addition of the above, acylglycerol lipase into the white water, or by the addition of so-called immobilized acylglycerol lipase or of the so-called immobilized microorganism capable of producing acylglycerol lipase extracellularly, wherein the immobilization of the enzyme or microorganism is carried out by the conventional method, such as carrier-binding-, cross-linking—, entrapment—method, etc.

Since the method of present invention causes a highly selective reaction known as an enzyme—reaction against triglyceride, and since this reaction is mild, the stock treated with the enzyme is not denatured so that the method of the present invention exerts no harm influence on the usual operation.

Pitch troubles occur in a complicate system comprising pulp' fibers, pitches, metal ions, fillers, etc. Although the reason for causing pitch troubles is not perfectly known, it is said that the pitch troubles depend upon various factors, such as pitch consistency, pulp consistency, pH-value, temperature, metal-ion consistency, metal—ion kinds and the like. In general.

-. • L <. • l^rmT'ri •trJ*J",V'"'''fT*T,|i , ,MM , I, , ,|||,, , _ ; 23163 an adsorption onto a solid surface is due to the exertion of Van der Waals-force which fixes the substance adhered onto a solid surface.

As the mutual interaction between the substance and the solidr there are various types of actions, among which a hydrophobic bond, a reciprocal action of dipole moments, etc. are important. And a hydrophobic or non-polar molecule or a hydrophobic molecule—portion is easily attracted to a hydrophobic or non-polar surface, whereas a hydrophilic or polar molecule is easily attracted to a polar surface.

Considering the mechanism for the pitch deposition in a pulp- or paper-making process, accordingly, tryglycerides play, the following roll. Through Van der Waals force, triglycerides, i,e. the non-polar constituent in colloidal pitch, adheres to the hydrophobic or non-polar surface, such as the metal surface of tank, pipe, etc.; the surface of the center roll of paper-making press section; and the like. The adhered portion exerts as a nucleus, to which the hydrophobic or non-polar molecules or the hydrophobic molecule-portions in pitch-constituents adhere successively to form the pitch deposits. © 2316 37 The mechanism for avoiding the pitch depositions according to the present invention is as follows. The acylglycerol lipase exerts on the non-polar tryglyceride which exits in pulp surface-pitch or in colloidal pitch (such as pitch in white water) and © which has high tackiness to the hydrophobic and non- polar surface, whereby triglyceride is hydrolyzed to water-soluble glycerol and polar fatty acid. Accordingly, the pitch depositions to hydrophobic surface of metal-pipes, chests, rolls, etc. are avoided. Since the pitch depositions are avoided in the early stage, the growth of the pitch deposits do not occur, which avoids pitch troubles.

The method of present invention has an advantage of avoiding pitch troubles, such as pitch spots and holes in a paper-web, etc., caused by pitch deposited in a process for the production of mechanical pulp and of mechanical pulp containing paper. Further, the method of the present invention has no harm effect on the paper qualities and the practical run, it is simplified and applied to a conventional pulp— and paper making process without installing additional equipments.

The present invention will be understood more readily with reference to the following examples. However, these examples are intended to illustrate the present invention and are not to be contrued to limit the scope of the present invention. Throughout the Examples, samples without enzyme-treatment are shown as "control".

[Example 1] Fresh Japanese red pine chip was extracted with methanol, using a soxhlet extractor. lOg of the obtained extracts were dissolved in a mixed solution of 10 0ml. isopropanol, 60ml acetone and 5ml water to obtain a pitch solution. - • 10ml of the pitch solution were charged in a beaker containing 11 of water and were dispersed under vigorous stirring to prepare a pitch dispersion. In such a manner, the resultant pitch was obtained in an yield of 4.7%, based on the weight of oven-dry chip, and it contained 37.8% triglycerides .

Then, the pH-value of the pitch dispersion was adjusted to 7 by adding hydrochloric acid and/or sodium hydroxide. The acylglycerol lipase was added thereto in different consistencies at various temperaturesr as shown in Table lr and was treated under gentle stirring for 4 hours to prepare a treated solution. In accordance with Tappi Routine Control Method RC-324, a cylinder built from polyethylene plate of 22cm width and -7cm length is setted 2.5cm above the water level. The adjusted solution was stirred for 30 minutes by using a Vibromixer (Irinitator, manufactured by U.S. Heidon Co.) Polyethylene-cylindrical plate was taken out and dried. The weight of tbe deposited pitch and the percentage to untreated pulp were indicated in Table 1. 2316 Table 1 Enzyme Temperature Kind Concentra-tion*4) °C 40°C 60°C Control 115mg (100%) 102mg (100%) 117mg (100%) 50ppm 93mg (80.9%) • Li. OF*1) 500ppm 58mg (50.4%) 35mg (30.4%) 90mg (78.3%) lOOOppm 28mg (24.3%) .

Li. A<2) 500ppm 66mg (57.4%) 54mg (47.0%) 96mg (83.5%) Li. P(3> 500ppm" 67mg (58.3%) 60mg (52.2%) 83mg (72.7%) (Note 1) Li,OF; trade name = Lipase OF (manufactured by Meitosangyo Co.), produced from Candida cylindracea.

(Note 2) Li,A; trade name = Lipase A (manufactured by Amano'Seiyaku Co.), produced from Aspergillus niger.

(Note 3) Li,P; trade name = Lipase P (manufactured by Amano Seiyaku Co.), produced from Pseudomonas fluorescens.

(Note 4) Concentation = Concentration of enzyme addition, based on pitch. r.: Z>&.'-<^:'->: - >" • - JVTCv^,' s -S ^ - CD 2316 37 [Example 2] The pH—value of the pitch dispersion was adjusted to 7 with hydrochloric acid and/or sodium hydroxide. The acylglycerol lipase was added thereto in an amount of 500ppm, based on the weight of pitch, and was stirred at 40°C. After a certain time, the amount of deposited pitch was obtained in the same manner as in Example 1 and was indicated in Table 2.

Table 2 Enzyme Temperature Kind Concentration 2hours 4hours 6hours Control 105mg (100%) lOlmg (100%) lOymg (100%) Li. OF 500ppm 67mg (63.8%) 31mg (30.7%) 3 ling (24.4%) Li. GC-(S) 500ppm 85mg. (8X10%} 70mg (69.3%) 59mg (55.1%) (Note 5) Li. GC-5; trade name : Lipase GC-5 (manufactured by Amano Seiyaku Co.), produced from Geotrichum candidum. 1 0 [Example 3] 11 of a slurry containing lOg GP of 63ml CSF(Canadian Standard Freeness) was prepared from Japanese red pine.

The acylglycerol lipases were added thereto in various consistencies and was treated under different pH-values in the same manner as in Example 1.

The amount of pitch deposited to polyethylene-cylindrical plate was measured as shown in Example lr and was indicated in Table 3.

O ■ © !o ® Table 3 Enzyme pH Kind Concentration'71 3 7 9 Control —— 118mg (100%) 112mg (100%) 102mg (100%) 121mg (100%) Li. OP lOpp * ■••MM 90mq (88.2%) 50 ppm 80mg (67.8%) 58mg (51.8%) 28mg (27.5%) 62mg (51.2%) 250ppm 21mg (20.6%) ■ ■WW Li. B<6> lOppm 96mg (79.3%) ,50ppm 95mg (80.5%) 65mg (58.3%) 42mg (41.2%) 27mg (22.3%) 250ppm 24mg (19.8%) Li. A 50ppm 84mg (71.2%) 66mg (58.9%) 49mg (48.0%) 88mg (72.7%) (40°C/ Treating period « 4 hours) (Note 6) Li, B; trade name » Lipase B (manufactured by SAPPORO BREWERIES LIMITED), produced from Pseudomonas fragi 22-39 B.

(Note 7) Concentration-"* Concentration of enzyme addition, based on the weight of pulp. 231637 [Example 4] The same sample as in Example 3 was used. The enzyme of the present invention was added to the sample I in an amount of 50ppm, based on the weight of pitch, and was treated in the same manner as in Example 1, at different temperatures and times. The amount of deposited pitch was measured and indicated in Table 4.

O; O '00 0 Table 4 Enzyme Temperature Kind P« Treating period °C 40°C 60°C Conbrol 7 115mg (100%) 102mg (100%) • H7mg (100%) Li. OP 2hours 44mg (53.9%) 4hours 64mg (55.7%) 29mg (28.4%) lOOmg (85.5%) 8hours 27mg (26.5%) Control 9 128mg (100%) 121mg (100%) • 134mg (100%) Li.B 2hours i 43mg (32.3%) 4hours 97mg (75.8%) 27mg (22.3%) 26mg (19.4%) 8houra 25mg (18.7%) ro —A, Ca8 23 1 [Example 5] 1% pulp slurry consisting of 20% of waste newspaper pulp (105 ml CSF), 25% of GP (63ml CSF), 25% of thermomechanical pulp (107ml CSF) and 30% of kraft pulp was prepared. 11 of this pulp slurry was used as sample. The enzyme of the present invention was added thereto in an amount of 50ppm, based on the weight of pulpT treated at 40°C for 4 hours, stirred for 120 minutes by a Vibromixer equipped with polyethylene cylindrical plate. The amount of deposited pitch was measured and indicated in Table 5.

Table 5 Amount of deposited pitch Control 65mg'(100%) Lipase OF 18mg (27.7%) [Example 6] 3£ of white water obtained by filtering Japanese red pine GP in a screening—stage were used as a sample. The enzyme of the present invention was added to the sample in an amount -of O.Sppm, based on the weight of the white water, treated at 40°C for 2 hours, and stirred with a Vibromixer for 120 minutes. The amount of pitch deposited to polyethylene cylindrical plate was measured and indicated in Table 6.

Table 6 Amount of deposited pitch Control 37mg (100%) Li. OF 7mg (18.9%) [Example 7] A newsprint paper of circa 46g/m2 bases weight was made by means of a Bel-Baie former multi-dryer paper machine with 5080mm width and 830m/min speed, wherein the paper stock consists of 30% GP, 45% waste newspaper pulp (deinked), 10% softwood KP and 15% thermomechanical pulp. 231637 D In this case, GP was prepared from red pine, and was adjusted to a freeness of 60-70 ml CSF by the post refining, storaged as a stock-pulp for a while, opitionally mixed with other pulps and anxiliaries,' again storaged and then fed to a paper—making process. (ps It takes 90 minutes from the post refiner through chests, tanks to the paper—making machine. The enzyme of the present invention was added to the GP slurry of 3.8% consistency before the post refiner so that Lipase OF has a concentration of 3ppm. The enzyme was continuously added to GP for two weeks.

There were determined the amounts of pitch deposited at the wire and press parts, and the interval between the removals of pitch deposited onto the center roll.. The practical output of the paper machine was-about 270 tons per day. The removal of pitch deposited on the center roll aims at preventing the excess pitch deposition for the good run, and the interval between the removals of pitch deposited onto the center roll is shorten with the increased amount of pitch deposits. The obtained results were compared with those of "control", and were indicated in Table 7.

Table 7 Control Li OF Amount of Max 895 89 pitch Min 73 0 deposited Aver 207 43 (g/day) age Interval Max 120 240 between the Min 120 removals of Aver 80 170 pitch age deposited (minutes) [Example 8] A light-weight printing paper of 34g/m2 basis weight was produced in accordance with Example 7, wherein the paper-stock consists of 20% GP,.50% waste newspaper pulp (deinked), 15% softwood RP and 15% thermomechanical pulp. Lipase OF was added to GP slurry in an amount of 3ppm. The practical output of the paper machine was about 200 tons per day. For the comparison with the results of "Control", there were determined the amount of pitch deposited in the wire and press parts, and the pitch holes of the paper due to pitch deposition at the breaker stack. The results were indicated in Table 8.

Table 8 Control Li OF Amount of Max 590 98 pitch Min 132 deposited Aver 221 47 (g/day) age Number of Max 65 14 pitch holes* Min 13 0 (per day) Aver 38 6 age * Expressed by number of small paper slips peeled off in the breaker stack. 2316

Claims (1)

WHAT WE CLAIM IS: (1) A method for avoiding pitch troubles in a process for the production of mechanical pulp and/or of mechanical pulp-containing.paper, which comprises treating the paper-stock and/or reused water by the addition of an acylglycerol lipase. said acylglycerol lipase is that produced from at least one microorganism selected from the group consisting of Aspergillus niger, Pseudomonas fluorescens, Pseudomonas fragi, Geotrichum candidum and Candida cylindracea. (3) The method according to Claim 1, wherein said acylglycerol lipase added to paper—stock slurry in an amount of O.l-lOOOOppm, based on the weight of mechanical pulp. (4) The method according to Claim 1, wherein the temperature of said paper-stock and/or reused water ranges from 10°t to 70°C. (5) The method according to Claim 1, wherein the temperature of said paper-stock and/or reused water ranges from 35°C to 55°C. (2) The method according to Claim 1, wherein 7 231637 (6) The method according to Claim 1, wherein the pH-value of said paper-stock and/or reused water ranges from 3 to 11. (7) A method for avoiding pitch troubles in a process for the production of mechanical pulp and/or of mechanical pulp-containing paper as defined in
1. Claim 1 substantially as herein described with reference to any example thereof. _____ DOTED-THIS DAY OF CV\oc*-AtgT*W * ' EA3K & SON J PER AGENTS FOR THE AWUCANTS