CA2051218A1 - Soft paper of high strength and method for production thereof - Google Patents
Soft paper of high strength and method for production thereofInfo
- Publication number
- CA2051218A1 CA2051218A1 CA002051218A CA2051218A CA2051218A1 CA 2051218 A1 CA2051218 A1 CA 2051218A1 CA 002051218 A CA002051218 A CA 002051218A CA 2051218 A CA2051218 A CA 2051218A CA 2051218 A1 CA2051218 A1 CA 2051218A1
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- paper
- fibre
- cellulosic
- wood
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000004519 manufacturing process Methods 0.000 title description 5
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 49
- 229910021653 sulphate ion Inorganic materials 0.000 claims abstract description 49
- 239000000203 mixture Substances 0.000 claims abstract description 30
- 229920001131 Pulp (paper) Polymers 0.000 claims abstract description 17
- 239000011122 softwood Substances 0.000 claims abstract description 17
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 claims abstract description 12
- 229920003043 Cellulose fiber Polymers 0.000 claims abstract description 10
- 239000011121 hardwood Substances 0.000 claims abstract description 10
- 239000010893 paper waste Substances 0.000 claims abstract description 9
- 239000003638 chemical reducing agent Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 11
- -1 ammonium ions Chemical class 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims 2
- 239000002023 wood Substances 0.000 description 55
- 235000018185 Betula X alpestris Nutrition 0.000 description 17
- 235000018212 Betula X uliginosa Nutrition 0.000 description 17
- 235000008331 Pinus X rigitaeda Nutrition 0.000 description 17
- 235000011613 Pinus brutia Nutrition 0.000 description 17
- 241000018646 Pinus brutia Species 0.000 description 17
- 239000000835 fiber Substances 0.000 description 9
- 230000015572 biosynthetic process Effects 0.000 description 7
- 210000001519 tissue Anatomy 0.000 description 6
- 241000878003 Dendrolycopodium obscurum Species 0.000 description 5
- 102100031260 Acyl-coenzyme A thioesterase THEM4 Human genes 0.000 description 4
- 101000638510 Homo sapiens Acyl-coenzyme A thioesterase THEM4 Proteins 0.000 description 4
- 241000218657 Picea Species 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 241000218631 Coniferophyta Species 0.000 description 2
- 244000166124 Eucalyptus globulus Species 0.000 description 2
- 241000183024 Populus tremula Species 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- BSYNRYMUTXBXSQ-UHFFFAOYSA-N Aspirin Chemical compound CC(=O)OC1=CC=CC=C1C(O)=O BSYNRYMUTXBXSQ-UHFFFAOYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 241000708948 Solva Species 0.000 description 1
- LZCDAPDGXCYOEH-UHFFFAOYSA-N adapalene Chemical compound C1=C(C(O)=O)C=CC2=CC(C3=CC=C(C(=C3)C34CC5CC(CC(C5)C3)C4)OC)=CC=C21 LZCDAPDGXCYOEH-UHFFFAOYSA-N 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 229940002658 differin Drugs 0.000 description 1
- 238000010410 dusting Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002430 hydrocarbons Chemical group 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 150000003856 quaternary ammonium compounds Chemical class 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
- D21H11/10—Mixtures of chemical and mechanical pulp
Landscapes
- Paper (AREA)
- Making Paper Articles (AREA)
- Sanitary Thin Papers (AREA)
Abstract
ABSTRACT
A paper having an advantageous combination of soft-ness and strength is disclosed, which is based on a mix-ture of cellulosic pulps and in which a) 55-90% by weight, of the total amount of cellulose fibres consists of a hardwood pulp, a waste paper pulp or a mechanical or semi-mechanical cellulosic pulp, or a mixture thereof, having a drainage resistance below 25°SR, and b) 10-45% by weight, of the total amount of cellulose fibres consists of a sulphite pulp and/or sulphate pulp based on softwood and having a drainage resistance exceeding 30°SR.
The paper can be produced by preparing a stock from the cellulosic pulps a) and b) in the above amounts, whereupon the stock is taken up on a wire, and is drained and dried in per se known manner.
A paper having an advantageous combination of soft-ness and strength is disclosed, which is based on a mix-ture of cellulosic pulps and in which a) 55-90% by weight, of the total amount of cellulose fibres consists of a hardwood pulp, a waste paper pulp or a mechanical or semi-mechanical cellulosic pulp, or a mixture thereof, having a drainage resistance below 25°SR, and b) 10-45% by weight, of the total amount of cellulose fibres consists of a sulphite pulp and/or sulphate pulp based on softwood and having a drainage resistance exceeding 30°SR.
The paper can be produced by preparing a stock from the cellulosic pulps a) and b) in the above amounts, whereupon the stock is taken up on a wire, and is drained and dried in per se known manner.
Description
2 ~ 8 SOFT PAPER OF HIGH STRENGT~ AND METHOD FOR
PRODUCTION THEREOF
The present invention concerns a soft but also strong paper which is based on a mixture of a hardwood pulp, a waste paper pulp or a mechanical or semi-mechanical cellu-losic pulp, or a mixture thereof, and a sulphate pulp and/or sulphite pulp based on softwood; as well as a method for the production thereof.
Usually, it is required that a soft paper, e.g. tis-sue paper, should be not only soft, but also strong. To achieve a satisfactory compromise between qualitative properties, such as softness and strength, on the one hand, and financial consideratlons, on the other hand, one has mixed different cellulosic pulps of differin~ origins and properties when producing soft paper, for example tissue paper. Generally, one main component is long-fibred to impart strength to the paper, while the other main component is short-fibred to give the paper its softness and the de~ired absorption qualities.
The long-fibred pulp is usually based on softwood, such as pine wood or spruc~ wood, which has been chemi-cally delignified by a sulphate or sulphite process. The short-fibred pulp is generally based on hardwood, such as birch wood, cucalyptus wood, aspen wood or oak wood, which has been delignified by a sulphato proceQS. At times, the celluloslc raw material may to a certain extent be based al30 on mechanical and semi-mechanical pulp, such as groundwood pulp, TMP and CTMP pulp and waste paper pulp.
The long-fibred pulps, or example chemical pulp from spruce wood or pine wood, has a fibre length of about 3-3c5 mm and a fibre width of about 0.04 mm. A short-fibred pulp based on birch sulphate has an average fibre length of 1.3 mm and a fibre thickness which is about half of that of conifer fibres. The proportion of short fibres, so-called fines, is high. Mechanical, semi-mechanical and waste fibre pulp have a fibre length which usually is '~5~2~
shorter than that of chemical pulp from spruce wood or pine wood. The proportion of fines may be high. When producing soft paper, it is desirable that the proportion of fines be kept as low as possible in order to reduce dusting.
To impart sultable paper-forming properties to the pulp, the latter is usually ground, e.g. in a beater or a refiner, which results in a paper of higher tensile strength. The degree of grinding i~ generally measured as the drainage resistance of the pulp according to Schopper-Riegler (SCAN C 19:65). The SR value increases with in-creasing grinding of the pulp. Already during the produc-tlon of cellulosic pulp for paper, the pulp usually is refined to 10-20SR.
When maklng tissue paper, the different pulps can be refined separately or in mixture. Grinding not only results in a higher tensile streng~h, but also in a higher tensile stiffness of the paper. Tahle 1 below illustrates this fact in connection with hand-made sheets of a mixture of 70~ birch sulphate and 30% pine sulphate pulp. In TAPPT
Journal 66 (2), 1983, pp 97-99, H. Hollmark states that the tensile stiffness of a paper correlates extremely well with softness determined by means of panel tests. The lower the tensile stiffness, the softer the paper, accord-ing to the test panel.
US Patent 2,706,155 discloses a method for producingsoft paper, the starting material being a mixture of 25-70% oak wood pulp, the remainder being softwood pulp.
The oak wood pulp is essentially unground, whereas the softwood pulp is refined. In an example, the softwood sulphate pulp was ground to 500 ml CSF, which corresponds to 25SR, and was then mixed with equal parts of essen-tlally unrefined oak wood sulphate pulp to achieve the desired combination of tensile strength, tearing strength, softness and absorption quali~ies of the paper.
~ ~3 ~
Soviet Patent 779,483 discloses the production of a paper from 40-60~ bleached softwood sulphate pulp, 30-54%
chemically refined aspen wood pulp and 5-15~ birch wood sulphate pulp which has been further chemically refined to increase the strength of the paper.
An article in the Soviet periodial Sb. Tr. TsNIIB
No. 15: 72-77 (1978) deals with hand-made sheets produced from softwood sulphite pulp, softwood sulphate pulp and hardwood sulphate pulp ground to 13-30SR, said sheets being tested as to absorption, compressibility, softness, ten~ile strength, bulk and strain. According to th~ ar-ticle, a three-component mixture consisting of 50% soft-wood sulphate pulp (<25SR), 30~ hardwood sulphate pulp (20-21S~) and 20~ sof~wood sulphite pulp (20-21SR) resulted in the tissue paper with the best properties.
Soviet Patent 775,212 states that tissue paper pro-duced rom a mixture of softwood sulphate pulp, hardwood sulphate pulp and softwood sulphite pulp ground to 23-25SR becomes softer if the softwood sulphate pulp has first been ground to 18-20SR.
SV 1,008,324 discloses the production of typographic paper of good opa ity and ink absorbency ~rom a paper-making pulp containlng 30-40~ by weight of bleached soft-wood sulphate pulp ground to 50-55SR and 60-70% by weight of hardwood sulphate pulp ground to 30-35SR.
One method of imparting increased softness to the paper is to treat the paper or the paper stock with a fibre-fibre-bond-rsducing agent, often called debonding agent. A fibre-fibre-bond-reducing agent usually comprises a prlmary, secondary, tertiary or quaternary ammonium com-pound containing a hydrocarbon group having 8-30 carbon atoms and, optionally, nonionic hydrophilic chains. It is common to combine ths cationic ammonium compound with a nonionlc surface-active compound. Such fibre-fibre-bond-reducing agen~ are inter alia described in US Patent Spe-cification~ 3,554,862, 3,554,863 and 4,144,122, as well as in GB Patent Specification 2,121,449. The fibre-fibre-~ i 2~ 8 bond-reducing agent markedly reduces the strength of the bonds between the fibres in the paper, while the softness increases. This is apparent from Table 1 bearing upon hand-made sheets from a mixture of 70% birch wood sulphate pulp and 30~ pine wood sulphate pulp. US Patent Specifica-tion 4,795,530 tries to solva tha inconvenience of strength reduction by applying the fibre-fibre-bond-reducing agent only to part of the thickness of the tissue paper, thereby to obtain an untreated part of paper maintaining its origlnal strength. As is apparent from Table 1 below, the changes in tensile stiffness and tensile strength of the paper owing to a conventional increased grinding of a pulp mixture and the addition of a fibre-flbre-bond-reducing agent to the ground fibre mixture cancel each other out. When grinding is increased, the strength and the stiffness increase proportionally.
When the amount of fibre-fibre-bond-reducing agent added is increased, the tensile stiffness as well as the tensile strength are proportionally reduced. Thus, the gain in strength is cancelled out by the loss in softness, and vice versa. There is, therefore, a generally expressed desire to improve the softness of a paper while main-taining a satisfac~ory strength.
It has now suprisingly been found that a paper advan-tageously combining softness and strength is obtained if b~sed on a mlxture of a) a hardwood pulp, a waste paper pulp or a mecha-nical or semi-mechanical celluloslc pulp, or a mixture thereof, constituting 55-90% by weight, of the total amount of cellulose fibres and having a drainage resist-ance below 25SR, and b) a sulphate pulp and/or sulphite pulp based on softwood and constituting 10-45% by weight, of the total amount of cellulose fibres and having a drainage resist-ance exceeding 30SR. The difference in drainage resist-ance between the cellulosic pulps b) and a) is preferably at least 10SR. The paper can be produced by preparing a ~ ~ r~
stock from the above cellulosic pulps a) and b) in the given amounts, whereupon the stock mixture is taken up on a w~re, and is drained and dried in per se known manner.
In a preferred embodiment, the soft paper also con-tains a fibre-fibre-bond-reducing agent in an amount of 0.05-2.5% by weight, as based on the amount of cellulose fibres. As mentioned earlier, a soft paper according to the invention has a surprisingly advantageous rat$o of softness to strength. To achieve this effect, the cellu-losic pulp b) should be ground to above 30SR, but prefer-ably not above 80SR, since pul~s of so high grinding degrees require comparatively large amount~ of fibre-fibre-bond-reducing agents to give the paper a satisfac-tory softness. The celluloslc pulp b) preferably has 35-60SR. The cellulosic pulp a) should be essentially un-ground or ground to less than 25SR, preferably less than 20SR.
Whether the long-fibred pulp b) has been obtained by a sulphate process or by a sulphite process is of no decisive $mportance. Also, whether it originates from pine wood, spruce wood or another conifer is of no vital impor-tance elther. It is, however, dssirable that it has been ground in such a manner that the fibres have been shorten-ed a~ little as possible. The grind$ng results in a fibre of higher flexibility. To benef$t from this increased flexibility of ~he long-fibred ground cellulosic pulp, there is preferably an addition of a fibre-fibre-bond-reduclng a~ent serving to reduce the increase in strength re~ulting ~rom the grinding, when the pulp forms a sheet of paper. The agent is added in such a manner as to be able to act on the bonds between the fibres. Prsferably, the addltlon takes place at a stage during the preparation of the stock, but the fibre-fibre-bond-reducing agent may also be added to the cellulosic pulp a) and/or the cellu-losic pulp b) or to the wet, formed or dried paper web.
~ 3 ~
Preparatlon of Hand-made Sheets and Measurin~ Techniques The cellulosic pulps were ground in a beater accord-ing to SCAN C 25:67 to the desired drainage resistance determined in a Schopper-Riegler apparatus according to SCAN Standard C 19:65. In those cases when one did not want to notlceably change the dra~nag~ resistance of the cellulosic pulp, the latter wa~ wet-defibrated according to ~CAN C 18:65.
Before the formation of sheets, the cellulosic pulp, alternatively the mixture of cellulosic pulp, was stirred, optionally in the presence of a fibre-fibre-bond-reducing agent, at a pulp concentration of about 2% by weight for 10 min. In the prsduction of sheets, use was made of tap water of 30C whose pH had been ad~usted to 6-7. The sheets were dried and conditloned according to SCAN P
2:75, whereupon the basis weight of the sheets was deter-mined according to SCAN P 6:63. When measuring tensile strength and tensile stiffnes~ according to SCAN P 44:81, but with 15 mm broad straps, ons used a tensile-strength tester of the mark Alwetron TH1, made by Lorentzen &
Wettre, Stockholm. The indices of tensile strength and tensile ~tiffnes~, respectively, were determined by dlvision by the basis weight of the she~t, in order to eliminate the influence thereof.
Comparison In the comparative study, plne wood sulphate pulp and birch wood sulphate pulp were mixed. The pulps, ground as bslow, were mixed in such a manner that 70% by weight con-sisted of birch wood sulphate pulp and 30% by weight con-slsted of pine wood sulphate pulp. Hand-made sheets were ~ormed in accordance wi~h the above-described method. The following results were obtained.
2 ~ c~ 8 Table 1 , Birch Plne Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 Without debonder 12 12 19.3 2780 6.9 Without debonder 18.5 18.5 35.6 5250 6.8 With, 2 kg ptp ) 18.5 18.5 32.3 4680 6.9 10 With, 4 kg ptp 18.5 18.5 28.0 3960 7.1 With, 16 kg ptp 18.5 18.5 19.9 2740 7.3 Wlthout debonder 26 26 55.0 7950 6.9 With, 2 kg ptp 26 26 38.3 5600 6.8 15 With, 4 kg ptp 26 26 30.6 4400 7.0 W~th, 16 kg ptp 26 26 22.3 3140 7.1 ~ ~ . _ , ) ptp = per ton pulp As is apparent from these results, an i~creased grinding of a pulp mixture combined with an addltion of fibre-fibre-bond-reducing agent to the ground fibre mix-ture does not noticeably affect the ratio of strength to stiffness (se~ the last column of the Table). When grinding is increased, the strength as well as the tensile stiffness are proportionally increased. When more of the flbre-flbre-bond-reducing agent is added, the tensile stiffness ls :reduced proportionally, as is the strength.
Thu~, the gain in tensile strength is cancelled out by a reduced softness, and vlce versa.
E~ample 1 A long-fibred pine wood sulphate pulp was ground to 13, 16.5, 20, 27 and 45SR. Then, 30 parts by weight of the long-fibred pulp was mixed with 70 parts by weight of short-fibred wet-defibrated birch wood sulphate pulp, whereupon hand-made shee~s were produced. The following results were obtalned.
~3r~ 2~8 Table 2 . .
Birch Pine Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index 5 (SR) (SR) (Nm/g) (Nm/g~ *1000 ~ . . . . .
Wlthout debonder 14 13 15.5 2240 6.9 Without debonder 14 16.5 18.7 2750 6.8 With, 4 kg ptp 14 16.5 12.2 1770 6.9 Wlthout debonder 14 20 21.5 3110 6.9 With, 4 kg ptp 14 20 14.8 2110 7.0 Without debonder 14 27 26.1 3640 7.2 15 Wlth, 4 kg ptp 14 27 15.3 2120 7.2 Without debonder 14 45 32.8 4050 8.1 With, 4 kg ptp 14 45 16.6 1750 9.5 As is apparent from these results, the ratlo strength/stiffness of the paper is roughly constant at a drainage resistance of 13-27SR of the pine wood pulp, but i5 considerably improved when pine wood pulp of 45SR is used~
Further, it can be seen that a stock containing pine wood pulp ground to a drainage resistance of 45SR and with an addition of a fibre-fibre-bond-reducing agent results in an even better ratio.
Example 2 A plne wood sulphate pulp according to Exa~ple 1 and ground as below was mixed with a short-fibred pulp con-sisting of a wet-defibrated eucalyptus wood sulphate pulp.
For the shee~ formation, use was made of a pulp mixture of 70% eucalyptus wood sulphate pulp and 30~ ground pine wood sulphate pulp~ The following results were obtained.
Table 3 -Euca- Pine Ten- Stiff- Strength/
lyp- wood slle ness Stiffness tus pulp index index wood pulp (SR) (SR) (Nm/g) (Nm/g) *1000 .
Without debonder 16 12 19.0 2740 6.9 10 Wlthout debonder 16 45 29;6 3620 8.2 With, 4 kg ptp 16 45 18.9 2100 9.0 ~ , .
From the above Table, it can b~ gathered that the ratio of tensile strength to tensile stiffness is advan~
tageous for the paper according to the invention.
Example 3 A spruce wood sulphite pulp ~round as below was mixed with a short-fibred wet-defibrated birch wood sulphate pulp. For the sheet formation, use was made of a pulp mix-ture of 70% birch wood sulphate pulp and 30% ground sprucewood sulphite pulp. The following results were obtained.
Table 4 Birch Spruce Ten- Stiff- Strength/
wood wood sion ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 ~ . _ Without debonder 13 12 18.0 2790 6.5 30 Without debonder 13 39 30.9 4510 6.9 With, 4 kg ptp 13 39 15.5 1990 7.8 Without debonder 13 47 33.2 4660 7.1 Wlth, 2 kg ptp 13 47 25.7 3420 7.5 35 With, 4 kg ptp 13 47 19.9 2520 7.9 2~ '1Y
From the above Table, it can be gathered that the ratlo of tenslle strength to tenslle stlffness also in this case is advantageous for the paper according to the invention.
Example 4 A long-fibred pine wood sulphate pulp ground as below was mixed with a short-flbred wet-defibrated birch wood sulphate pulp. For the sheet formation, use was made of a pulp mixture of 80% birch wood sulphate pulp and 20%
ground pine wood sulphate pulp. The following results were obtained.
Table 5 ~ ~ .
Birch Plne Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 , Without debonder 14 12 18.1 2830 6.4 20 Without debonder 14 28 22.3 3410 6.5 With, 4 kg ptp 14 28 11.4 1630 6.7 Without debonder 14 46 27.4 3530 7.8 With, 4 kg ptp 14 46 14.7 2030 7.9 ~
It i8 apparent from these result~ that the ratio of ten~ile strength to tensile stiffness is advantageous when the paper has a composition according to the invention.
Example 5 A pine wood sulphate pulp ground as below was mixed with a short-fibred wet-defibrated birch wood sulphate pulp.
For the sheet formation, use was made of a pulp mixture of 60% birch wood sulphate pulp and 40% ground pine wood sul-phate pulp. The following results were obtained.
J 'i 2 ~ ~
Table 6 Birch Plne Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 . . . ~ . .
Without debonder 14 12 19.1 2750 6.9 Without debonder 14 28 25.5 3640 7.0 With, 4 kg ptp 14 28 16.7 2350 7.1 Without debonder 14 46 34.5 3970 8.7 With, 4 kg ptp 14 46 24.3 2620 9.3 _ As ls apparent from these results, the ratio of ten-sile strength to tensile stiffness is advantageous when the paper has a compositlon according to the inventlon.
Example 6 A pine wood sulphate pulp ground as below w~s mixed with a deinked waste-paper-based pulp. The pulp had been produced ln a deinklng plant, the waste paper consis~ing of computer printouts, boo~s, brochures and the like. For the sheet formation, use was made of a pulp mixture of 70% waste paper pulp and 30~ ground pine wood sulphate pulp. The followlng results were obtained.
Tabls 7 Waste Pine Ten- Stiff- Strength/
paper wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 Without debonder 24 12 32.0 4100 7.8 Without debonder 24 45 39.6 4660 8.5 With, 4 kg ptp 24 45 33.8 4020 8.4 35 With, 8 kg ptp 24 45 32.4 3700 8.8 With, 16 kg ptp 24 45 24.6 2660 9.2 2~21~
It is apparent from these results that the ratio of tenslle strength to tenslle stiffness is advantageous when the paper has a composition according to the invention.
Example 7 A pine wood sulphate pulp ground as below was mixed with a wst-defibrated CTMP pulp. For the sheet formation, use was made of a pulp mixture of 70% CTMP and 30% ground pine wood sulphate pulp. The following results were obtained.
Table 8 CTMP Plne Ten- Stlff- Strength/
pulp wood sile ness 5tiffness pulp index index _ (SR) (SR) (Nm/g) (Nm/g) *1000 Wlthout debonder 11 12 18.2 2200 8.3 Without debonder 11 45 31.6 2900 10.9 With, 4 k~ ptp 11 45 21.6 2090 10.3 20 Wit~, 6 kg ptp 11 45 17.5 1650 10.6 ~ . -- . . .
It is apparent from these results that the ratio of tenslle strength to tensile stiffnss~ i~ advantageous when the paper ha~ a composition according to the invention.
PRODUCTION THEREOF
The present invention concerns a soft but also strong paper which is based on a mixture of a hardwood pulp, a waste paper pulp or a mechanical or semi-mechanical cellu-losic pulp, or a mixture thereof, and a sulphate pulp and/or sulphite pulp based on softwood; as well as a method for the production thereof.
Usually, it is required that a soft paper, e.g. tis-sue paper, should be not only soft, but also strong. To achieve a satisfactory compromise between qualitative properties, such as softness and strength, on the one hand, and financial consideratlons, on the other hand, one has mixed different cellulosic pulps of differin~ origins and properties when producing soft paper, for example tissue paper. Generally, one main component is long-fibred to impart strength to the paper, while the other main component is short-fibred to give the paper its softness and the de~ired absorption qualities.
The long-fibred pulp is usually based on softwood, such as pine wood or spruc~ wood, which has been chemi-cally delignified by a sulphate or sulphite process. The short-fibred pulp is generally based on hardwood, such as birch wood, cucalyptus wood, aspen wood or oak wood, which has been delignified by a sulphato proceQS. At times, the celluloslc raw material may to a certain extent be based al30 on mechanical and semi-mechanical pulp, such as groundwood pulp, TMP and CTMP pulp and waste paper pulp.
The long-fibred pulps, or example chemical pulp from spruce wood or pine wood, has a fibre length of about 3-3c5 mm and a fibre width of about 0.04 mm. A short-fibred pulp based on birch sulphate has an average fibre length of 1.3 mm and a fibre thickness which is about half of that of conifer fibres. The proportion of short fibres, so-called fines, is high. Mechanical, semi-mechanical and waste fibre pulp have a fibre length which usually is '~5~2~
shorter than that of chemical pulp from spruce wood or pine wood. The proportion of fines may be high. When producing soft paper, it is desirable that the proportion of fines be kept as low as possible in order to reduce dusting.
To impart sultable paper-forming properties to the pulp, the latter is usually ground, e.g. in a beater or a refiner, which results in a paper of higher tensile strength. The degree of grinding i~ generally measured as the drainage resistance of the pulp according to Schopper-Riegler (SCAN C 19:65). The SR value increases with in-creasing grinding of the pulp. Already during the produc-tlon of cellulosic pulp for paper, the pulp usually is refined to 10-20SR.
When maklng tissue paper, the different pulps can be refined separately or in mixture. Grinding not only results in a higher tensile streng~h, but also in a higher tensile stiffness of the paper. Tahle 1 below illustrates this fact in connection with hand-made sheets of a mixture of 70~ birch sulphate and 30% pine sulphate pulp. In TAPPT
Journal 66 (2), 1983, pp 97-99, H. Hollmark states that the tensile stiffness of a paper correlates extremely well with softness determined by means of panel tests. The lower the tensile stiffness, the softer the paper, accord-ing to the test panel.
US Patent 2,706,155 discloses a method for producingsoft paper, the starting material being a mixture of 25-70% oak wood pulp, the remainder being softwood pulp.
The oak wood pulp is essentially unground, whereas the softwood pulp is refined. In an example, the softwood sulphate pulp was ground to 500 ml CSF, which corresponds to 25SR, and was then mixed with equal parts of essen-tlally unrefined oak wood sulphate pulp to achieve the desired combination of tensile strength, tearing strength, softness and absorption quali~ies of the paper.
~ ~3 ~
Soviet Patent 779,483 discloses the production of a paper from 40-60~ bleached softwood sulphate pulp, 30-54%
chemically refined aspen wood pulp and 5-15~ birch wood sulphate pulp which has been further chemically refined to increase the strength of the paper.
An article in the Soviet periodial Sb. Tr. TsNIIB
No. 15: 72-77 (1978) deals with hand-made sheets produced from softwood sulphite pulp, softwood sulphate pulp and hardwood sulphate pulp ground to 13-30SR, said sheets being tested as to absorption, compressibility, softness, ten~ile strength, bulk and strain. According to th~ ar-ticle, a three-component mixture consisting of 50% soft-wood sulphate pulp (<25SR), 30~ hardwood sulphate pulp (20-21S~) and 20~ sof~wood sulphite pulp (20-21SR) resulted in the tissue paper with the best properties.
Soviet Patent 775,212 states that tissue paper pro-duced rom a mixture of softwood sulphate pulp, hardwood sulphate pulp and softwood sulphite pulp ground to 23-25SR becomes softer if the softwood sulphate pulp has first been ground to 18-20SR.
SV 1,008,324 discloses the production of typographic paper of good opa ity and ink absorbency ~rom a paper-making pulp containlng 30-40~ by weight of bleached soft-wood sulphate pulp ground to 50-55SR and 60-70% by weight of hardwood sulphate pulp ground to 30-35SR.
One method of imparting increased softness to the paper is to treat the paper or the paper stock with a fibre-fibre-bond-rsducing agent, often called debonding agent. A fibre-fibre-bond-reducing agent usually comprises a prlmary, secondary, tertiary or quaternary ammonium com-pound containing a hydrocarbon group having 8-30 carbon atoms and, optionally, nonionic hydrophilic chains. It is common to combine ths cationic ammonium compound with a nonionlc surface-active compound. Such fibre-fibre-bond-reducing agen~ are inter alia described in US Patent Spe-cification~ 3,554,862, 3,554,863 and 4,144,122, as well as in GB Patent Specification 2,121,449. The fibre-fibre-~ i 2~ 8 bond-reducing agent markedly reduces the strength of the bonds between the fibres in the paper, while the softness increases. This is apparent from Table 1 bearing upon hand-made sheets from a mixture of 70% birch wood sulphate pulp and 30~ pine wood sulphate pulp. US Patent Specifica-tion 4,795,530 tries to solva tha inconvenience of strength reduction by applying the fibre-fibre-bond-reducing agent only to part of the thickness of the tissue paper, thereby to obtain an untreated part of paper maintaining its origlnal strength. As is apparent from Table 1 below, the changes in tensile stiffness and tensile strength of the paper owing to a conventional increased grinding of a pulp mixture and the addition of a fibre-flbre-bond-reducing agent to the ground fibre mixture cancel each other out. When grinding is increased, the strength and the stiffness increase proportionally.
When the amount of fibre-fibre-bond-reducing agent added is increased, the tensile stiffness as well as the tensile strength are proportionally reduced. Thus, the gain in strength is cancelled out by the loss in softness, and vice versa. There is, therefore, a generally expressed desire to improve the softness of a paper while main-taining a satisfac~ory strength.
It has now suprisingly been found that a paper advan-tageously combining softness and strength is obtained if b~sed on a mlxture of a) a hardwood pulp, a waste paper pulp or a mecha-nical or semi-mechanical celluloslc pulp, or a mixture thereof, constituting 55-90% by weight, of the total amount of cellulose fibres and having a drainage resist-ance below 25SR, and b) a sulphate pulp and/or sulphite pulp based on softwood and constituting 10-45% by weight, of the total amount of cellulose fibres and having a drainage resist-ance exceeding 30SR. The difference in drainage resist-ance between the cellulosic pulps b) and a) is preferably at least 10SR. The paper can be produced by preparing a ~ ~ r~
stock from the above cellulosic pulps a) and b) in the given amounts, whereupon the stock mixture is taken up on a w~re, and is drained and dried in per se known manner.
In a preferred embodiment, the soft paper also con-tains a fibre-fibre-bond-reducing agent in an amount of 0.05-2.5% by weight, as based on the amount of cellulose fibres. As mentioned earlier, a soft paper according to the invention has a surprisingly advantageous rat$o of softness to strength. To achieve this effect, the cellu-losic pulp b) should be ground to above 30SR, but prefer-ably not above 80SR, since pul~s of so high grinding degrees require comparatively large amount~ of fibre-fibre-bond-reducing agents to give the paper a satisfac-tory softness. The celluloslc pulp b) preferably has 35-60SR. The cellulosic pulp a) should be essentially un-ground or ground to less than 25SR, preferably less than 20SR.
Whether the long-fibred pulp b) has been obtained by a sulphate process or by a sulphite process is of no decisive $mportance. Also, whether it originates from pine wood, spruce wood or another conifer is of no vital impor-tance elther. It is, however, dssirable that it has been ground in such a manner that the fibres have been shorten-ed a~ little as possible. The grind$ng results in a fibre of higher flexibility. To benef$t from this increased flexibility of ~he long-fibred ground cellulosic pulp, there is preferably an addition of a fibre-fibre-bond-reduclng a~ent serving to reduce the increase in strength re~ulting ~rom the grinding, when the pulp forms a sheet of paper. The agent is added in such a manner as to be able to act on the bonds between the fibres. Prsferably, the addltlon takes place at a stage during the preparation of the stock, but the fibre-fibre-bond-reducing agent may also be added to the cellulosic pulp a) and/or the cellu-losic pulp b) or to the wet, formed or dried paper web.
~ 3 ~
Preparatlon of Hand-made Sheets and Measurin~ Techniques The cellulosic pulps were ground in a beater accord-ing to SCAN C 25:67 to the desired drainage resistance determined in a Schopper-Riegler apparatus according to SCAN Standard C 19:65. In those cases when one did not want to notlceably change the dra~nag~ resistance of the cellulosic pulp, the latter wa~ wet-defibrated according to ~CAN C 18:65.
Before the formation of sheets, the cellulosic pulp, alternatively the mixture of cellulosic pulp, was stirred, optionally in the presence of a fibre-fibre-bond-reducing agent, at a pulp concentration of about 2% by weight for 10 min. In the prsduction of sheets, use was made of tap water of 30C whose pH had been ad~usted to 6-7. The sheets were dried and conditloned according to SCAN P
2:75, whereupon the basis weight of the sheets was deter-mined according to SCAN P 6:63. When measuring tensile strength and tensile stiffnes~ according to SCAN P 44:81, but with 15 mm broad straps, ons used a tensile-strength tester of the mark Alwetron TH1, made by Lorentzen &
Wettre, Stockholm. The indices of tensile strength and tensile ~tiffnes~, respectively, were determined by dlvision by the basis weight of the she~t, in order to eliminate the influence thereof.
Comparison In the comparative study, plne wood sulphate pulp and birch wood sulphate pulp were mixed. The pulps, ground as bslow, were mixed in such a manner that 70% by weight con-sisted of birch wood sulphate pulp and 30% by weight con-slsted of pine wood sulphate pulp. Hand-made sheets were ~ormed in accordance wi~h the above-described method. The following results were obtained.
2 ~ c~ 8 Table 1 , Birch Plne Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 Without debonder 12 12 19.3 2780 6.9 Without debonder 18.5 18.5 35.6 5250 6.8 With, 2 kg ptp ) 18.5 18.5 32.3 4680 6.9 10 With, 4 kg ptp 18.5 18.5 28.0 3960 7.1 With, 16 kg ptp 18.5 18.5 19.9 2740 7.3 Wlthout debonder 26 26 55.0 7950 6.9 With, 2 kg ptp 26 26 38.3 5600 6.8 15 With, 4 kg ptp 26 26 30.6 4400 7.0 W~th, 16 kg ptp 26 26 22.3 3140 7.1 ~ ~ . _ , ) ptp = per ton pulp As is apparent from these results, an i~creased grinding of a pulp mixture combined with an addltion of fibre-fibre-bond-reducing agent to the ground fibre mix-ture does not noticeably affect the ratio of strength to stiffness (se~ the last column of the Table). When grinding is increased, the strength as well as the tensile stiffness are proportionally increased. When more of the flbre-flbre-bond-reducing agent is added, the tensile stiffness ls :reduced proportionally, as is the strength.
Thu~, the gain in tensile strength is cancelled out by a reduced softness, and vlce versa.
E~ample 1 A long-fibred pine wood sulphate pulp was ground to 13, 16.5, 20, 27 and 45SR. Then, 30 parts by weight of the long-fibred pulp was mixed with 70 parts by weight of short-fibred wet-defibrated birch wood sulphate pulp, whereupon hand-made shee~s were produced. The following results were obtalned.
~3r~ 2~8 Table 2 . .
Birch Pine Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index 5 (SR) (SR) (Nm/g) (Nm/g~ *1000 ~ . . . . .
Wlthout debonder 14 13 15.5 2240 6.9 Without debonder 14 16.5 18.7 2750 6.8 With, 4 kg ptp 14 16.5 12.2 1770 6.9 Wlthout debonder 14 20 21.5 3110 6.9 With, 4 kg ptp 14 20 14.8 2110 7.0 Without debonder 14 27 26.1 3640 7.2 15 Wlth, 4 kg ptp 14 27 15.3 2120 7.2 Without debonder 14 45 32.8 4050 8.1 With, 4 kg ptp 14 45 16.6 1750 9.5 As is apparent from these results, the ratlo strength/stiffness of the paper is roughly constant at a drainage resistance of 13-27SR of the pine wood pulp, but i5 considerably improved when pine wood pulp of 45SR is used~
Further, it can be seen that a stock containing pine wood pulp ground to a drainage resistance of 45SR and with an addition of a fibre-fibre-bond-reducing agent results in an even better ratio.
Example 2 A plne wood sulphate pulp according to Exa~ple 1 and ground as below was mixed with a short-fibred pulp con-sisting of a wet-defibrated eucalyptus wood sulphate pulp.
For the shee~ formation, use was made of a pulp mixture of 70% eucalyptus wood sulphate pulp and 30~ ground pine wood sulphate pulp~ The following results were obtained.
Table 3 -Euca- Pine Ten- Stiff- Strength/
lyp- wood slle ness Stiffness tus pulp index index wood pulp (SR) (SR) (Nm/g) (Nm/g) *1000 .
Without debonder 16 12 19.0 2740 6.9 10 Wlthout debonder 16 45 29;6 3620 8.2 With, 4 kg ptp 16 45 18.9 2100 9.0 ~ , .
From the above Table, it can b~ gathered that the ratio of tensile strength to tensile stiffness is advan~
tageous for the paper according to the invention.
Example 3 A spruce wood sulphite pulp ~round as below was mixed with a short-fibred wet-defibrated birch wood sulphate pulp. For the sheet formation, use was made of a pulp mix-ture of 70% birch wood sulphate pulp and 30% ground sprucewood sulphite pulp. The following results were obtained.
Table 4 Birch Spruce Ten- Stiff- Strength/
wood wood sion ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 ~ . _ Without debonder 13 12 18.0 2790 6.5 30 Without debonder 13 39 30.9 4510 6.9 With, 4 kg ptp 13 39 15.5 1990 7.8 Without debonder 13 47 33.2 4660 7.1 Wlth, 2 kg ptp 13 47 25.7 3420 7.5 35 With, 4 kg ptp 13 47 19.9 2520 7.9 2~ '1Y
From the above Table, it can be gathered that the ratlo of tenslle strength to tenslle stlffness also in this case is advantageous for the paper according to the invention.
Example 4 A long-fibred pine wood sulphate pulp ground as below was mixed with a short-flbred wet-defibrated birch wood sulphate pulp. For the sheet formation, use was made of a pulp mixture of 80% birch wood sulphate pulp and 20%
ground pine wood sulphate pulp. The following results were obtained.
Table 5 ~ ~ .
Birch Plne Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 , Without debonder 14 12 18.1 2830 6.4 20 Without debonder 14 28 22.3 3410 6.5 With, 4 kg ptp 14 28 11.4 1630 6.7 Without debonder 14 46 27.4 3530 7.8 With, 4 kg ptp 14 46 14.7 2030 7.9 ~
It i8 apparent from these result~ that the ratio of ten~ile strength to tensile stiffness is advantageous when the paper has a composition according to the invention.
Example 5 A pine wood sulphate pulp ground as below was mixed with a short-fibred wet-defibrated birch wood sulphate pulp.
For the sheet formation, use was made of a pulp mixture of 60% birch wood sulphate pulp and 40% ground pine wood sul-phate pulp. The following results were obtained.
J 'i 2 ~ ~
Table 6 Birch Plne Ten- Stiff- Strength/
wood wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 . . . ~ . .
Without debonder 14 12 19.1 2750 6.9 Without debonder 14 28 25.5 3640 7.0 With, 4 kg ptp 14 28 16.7 2350 7.1 Without debonder 14 46 34.5 3970 8.7 With, 4 kg ptp 14 46 24.3 2620 9.3 _ As ls apparent from these results, the ratio of ten-sile strength to tensile stiffness is advantageous when the paper has a compositlon according to the inventlon.
Example 6 A pine wood sulphate pulp ground as below w~s mixed with a deinked waste-paper-based pulp. The pulp had been produced ln a deinklng plant, the waste paper consis~ing of computer printouts, boo~s, brochures and the like. For the sheet formation, use was made of a pulp mixture of 70% waste paper pulp and 30~ ground pine wood sulphate pulp. The followlng results were obtained.
Tabls 7 Waste Pine Ten- Stiff- Strength/
paper wood sile ness Stiffness pulp pulp index index (SR) (SR) (Nm/g) (Nm/g) *1000 Without debonder 24 12 32.0 4100 7.8 Without debonder 24 45 39.6 4660 8.5 With, 4 kg ptp 24 45 33.8 4020 8.4 35 With, 8 kg ptp 24 45 32.4 3700 8.8 With, 16 kg ptp 24 45 24.6 2660 9.2 2~21~
It is apparent from these results that the ratio of tenslle strength to tenslle stiffness is advantageous when the paper has a composition according to the invention.
Example 7 A pine wood sulphate pulp ground as below was mixed with a wst-defibrated CTMP pulp. For the sheet formation, use was made of a pulp mixture of 70% CTMP and 30% ground pine wood sulphate pulp. The following results were obtained.
Table 8 CTMP Plne Ten- Stlff- Strength/
pulp wood sile ness 5tiffness pulp index index _ (SR) (SR) (Nm/g) (Nm/g) *1000 Wlthout debonder 11 12 18.2 2200 8.3 Without debonder 11 45 31.6 2900 10.9 With, 4 k~ ptp 11 45 21.6 2090 10.3 20 Wit~, 6 kg ptp 11 45 17.5 1650 10.6 ~ . -- . . .
It is apparent from these results that the ratio of tenslle strength to tensile stiffnss~ i~ advantageous when the paper ha~ a composition according to the invention.
Claims (10)
- l. Paper having an advantageous combination of soft-ness and strength and based on a mixture of cellulosic pulps, c h a r a c t e r i s e d in that a) 55-90% by weight, of the total amount of cellulose fibres consists of a hardwood pulp, a waste paper pulp or a mechanical or semi-mechanical cellulosic pulp, or a mixture thereof, having a drainage resistance below 25°SR, and b) 10-45% by weight, of the total amount of cellulose fibres consists of a sulphite pulp and/or sulphate pulp based on softwood and having a drainage resistance ex-ceeding 30°SR.
- 2. Paper as claimed in claim 1, c h a r a c t e r -i s e d in that the cellulosic pulp b) has a drainage resistance not exceeding 80°SR.
- 3. Paper as claimed in claim 1 or 2, c h a r a c -t e r 1 s e d in that the cellulosic pulp b) has a drain-age resistance of 35-60°SR.
- 4. Paper as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the cellulosic pulp a) has a drainage resistance below 20°SR.
- 5. Paper as claimed in any one of claims 1-4, c a h a r a c t e r i s e d in that it contains a fibre-fibre-bond-reducing agent.
- 6. Paper as claimed in claim 5, c h a r a c t e r -i s e d in that the fibre-fibre-bond-reducing agent con-tains a compound with ammonium ions.
- 7. Paper as claimed in claim 5 or 6, c h a r a c -t e r i s e d in that it contains 0.05-2.5% by weight of said fibre-fibre-bond-reducing agent.
- 8. Method of producing paper according to any one of claim 1-7, c h a r a c t e r i 5 e d in that a stock is prepared from a) a hardwood pulp, a waste paper pulp or a mecha-nical or semi-mechanical cellulosic pulp, or a mixture thereof, having a drainage resistance below 25°SR, and is mixed with b) a sulphite pulp and/or sulphate pulp based on softwood and having a drainage resistance exceeding 30°SR, the cellulosic pulp a) constituting 55-90% by weight of the total amount of cellulose fibres, and the cellulosic pulp b) constituting 10-45% by weight of the total amount of cellulose fibres, whereupon the stock mixture is taken up on a wire, and is drained and dried in per se known manner.
- 9. Method as claimed in claim 8, c h a r a c t e r -i s e d in that the cellulosic pulp a) has a drainage resistance below 20°SR, and that the cellulosic pulp b) has a drainage resistance of 35-60°SR.
- 10. Method as claimed in claim 8 or 9, c h a r a c -t e r i s e d by the addition, at some stage, of a fibre-fibre-bond-reducing agent preferably containing a compound with ammonium ions and preferably being present in an amount of 0.05-2.5% by weight, as based on the amount of cellulose fibres.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9002900-0 | 1990-09-12 | ||
| SE9002900A SE500524C2 (en) | 1990-09-12 | 1990-09-12 | Soft paper with high strength and process for its preparation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2051218A1 true CA2051218A1 (en) | 1992-03-13 |
Family
ID=20380335
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002051218A Abandoned CA2051218A1 (en) | 1990-09-12 | 1991-09-12 | Soft paper of high strength and method for production thereof |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0478045B1 (en) |
| AT (1) | ATE119595T1 (en) |
| AU (1) | AU636059B2 (en) |
| CA (1) | CA2051218A1 (en) |
| DE (1) | DE69107940T2 (en) |
| ES (1) | ES2069819T3 (en) |
| FI (1) | FI96335C (en) |
| NO (1) | NO177938C (en) |
| NZ (1) | NZ239562A (en) |
| SE (1) | SE500524C2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE504030C2 (en) * | 1995-02-17 | 1996-10-21 | Moelnlycke Ab | High bulk spun lace material and absorbency as well as process for its preparation |
| SE505388C2 (en) * | 1995-11-24 | 1997-08-18 | Sca Hygiene Paper Ab | Soft, bulky, absorbent paper containing chemitermomechanical pulp |
| FI119562B (en) * | 2000-02-07 | 2008-12-31 | Upm Kymmene Corp | Fluff, process for making fluff, using fluff, and product made from fluff |
| CN100427680C (en) * | 2006-04-15 | 2008-10-22 | 永州湘江纸业有限责任公司 | High-temp. hot-pressing type bedding paper and its prodn. method |
| PT115562B (en) | 2019-06-03 | 2021-12-24 | Raiz Instituto De Investig Da Floresta E Papel | EUCALYPTUS GLOBULUS PEEL PULP AND ITS PRODUCTION PROCESS FOR TISSUE PAPER PRODUCTS |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2706155A (en) * | 1951-10-24 | 1955-04-12 | Camp Mfg Company Inc | Absorbent paper |
| GB1117731A (en) * | 1963-09-17 | 1968-06-26 | Wycombe Marsh Paper Mills Ltd | Two-layer paper |
| SE7602750L (en) * | 1975-03-03 | 1976-09-06 | Procter & Gamble | USE OF THERMOMECHANICAL PULP FOR THE MANUFACTURE OF HIGH BULK TISSUE |
-
1990
- 1990-09-12 SE SE9002900A patent/SE500524C2/en unknown
-
1991
- 1991-08-27 NZ NZ239562A patent/NZ239562A/en unknown
- 1991-09-02 NO NO913436A patent/NO177938C/en not_active IP Right Cessation
- 1991-09-10 ES ES91202328T patent/ES2069819T3/en not_active Expired - Lifetime
- 1991-09-10 AT AT91202328T patent/ATE119595T1/en not_active IP Right Cessation
- 1991-09-10 DE DE69107940T patent/DE69107940T2/en not_active Expired - Fee Related
- 1991-09-10 FI FI914269A patent/FI96335C/en active
- 1991-09-10 EP EP91202328A patent/EP0478045B1/en not_active Expired - Lifetime
- 1991-09-11 AU AU83775/91A patent/AU636059B2/en not_active Ceased
- 1991-09-12 CA CA002051218A patent/CA2051218A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| FI914269A (en) | 1992-03-13 |
| AU636059B2 (en) | 1993-04-08 |
| DE69107940D1 (en) | 1995-04-13 |
| EP0478045B1 (en) | 1995-03-08 |
| NO913436D0 (en) | 1991-09-02 |
| AU8377591A (en) | 1992-03-19 |
| NO913436L (en) | 1992-03-13 |
| SE500524C2 (en) | 1994-07-11 |
| FI914269A0 (en) | 1991-09-10 |
| SE9002900L (en) | 1992-03-13 |
| EP0478045A1 (en) | 1992-04-01 |
| ES2069819T3 (en) | 1995-05-16 |
| SE9002900D0 (en) | 1990-09-12 |
| FI96335C (en) | 1996-06-10 |
| NZ239562A (en) | 1992-11-25 |
| NO177938C (en) | 1995-12-20 |
| NO177938B (en) | 1995-09-11 |
| ATE119595T1 (en) | 1995-03-15 |
| DE69107940T2 (en) | 1995-07-13 |
| FI96335B (en) | 1996-02-29 |
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