EP0038136B1 - Fibrous materials - Google Patents
Fibrous materials Download PDFInfo
- Publication number
- EP0038136B1 EP0038136B1 EP81301359A EP81301359A EP0038136B1 EP 0038136 B1 EP0038136 B1 EP 0038136B1 EP 81301359 A EP81301359 A EP 81301359A EP 81301359 A EP81301359 A EP 81301359A EP 0038136 B1 EP0038136 B1 EP 0038136B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- fibres
- weight
- amino
- formaldehyde resin
- fibre
- 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.)
- Expired
Links
- 239000002657 fibrous material Substances 0.000 title claims description 27
- 229920005989 resin Polymers 0.000 claims description 73
- 239000011347 resin Substances 0.000 claims description 73
- 239000000835 fiber Substances 0.000 claims description 65
- ZHNUHDYFZUAESO-OUBTZVSYSA-N aminoformaldehyde Chemical compound N[13CH]=O ZHNUHDYFZUAESO-OUBTZVSYSA-N 0.000 claims description 59
- 238000000034 method Methods 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 229920003043 Cellulose fiber Polymers 0.000 claims description 21
- 239000000203 mixture Substances 0.000 claims description 19
- 230000008569 process Effects 0.000 claims description 19
- 238000010438 heat treatment Methods 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 9
- 238000001914 filtration Methods 0.000 claims description 2
- 239000003795 chemical substances by application Substances 0.000 claims 1
- 230000001737 promoting effect Effects 0.000 claims 1
- 239000000123 paper Substances 0.000 description 53
- 229920002678 cellulose Polymers 0.000 description 18
- 239000001913 cellulose Substances 0.000 description 18
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 15
- 229920001807 Urea-formaldehyde Polymers 0.000 description 15
- ODGAOXROABLFNM-UHFFFAOYSA-N polynoxylin Chemical compound O=C.NC(N)=O ODGAOXROABLFNM-UHFFFAOYSA-N 0.000 description 11
- 239000000523 sample Substances 0.000 description 10
- -1 amino compound Chemical class 0.000 description 9
- 238000009987 spinning Methods 0.000 description 9
- GZCGUPFRVQAUEE-SLPGGIOYSA-N aldehydo-D-glucose Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O GZCGUPFRVQAUEE-SLPGGIOYSA-N 0.000 description 8
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 6
- 238000003825 pressing Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 229910021653 sulphate ion Inorganic materials 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 229920000139 polyethylene terephthalate Polymers 0.000 description 5
- 239000005020 polyethylene terephthalate Substances 0.000 description 5
- 229920001131 Pulp (paper) Polymers 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 238000010348 incorporation Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000010561 standard procedure Methods 0.000 description 4
- 235000018185 Betula X alpestris Nutrition 0.000 description 3
- 235000018212 Betula X uliginosa Nutrition 0.000 description 3
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 3
- 238000010009 beating Methods 0.000 description 3
- 239000004202 carbamide Substances 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 239000012634 fragment Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- 229920000877 Melamine resin Polymers 0.000 description 2
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 2
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 2
- 239000001166 ammonium sulphate Substances 0.000 description 2
- 235000011130 ammonium sulphate Nutrition 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229920005610 lignin Polymers 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 2
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- 229920000742 Cotton Polymers 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical class Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 229920003180 amino resin Polymers 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009172 bursting Effects 0.000 description 1
- 150000001720 carbohydrates Chemical class 0.000 description 1
- 235000014633 carbohydrates Nutrition 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000000875 corresponding effect Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000578 dry spinning Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 239000011121 hardwood Substances 0.000 description 1
- 231100000206 health hazard Toxicity 0.000 description 1
- 235000011167 hydrochloric acid Nutrition 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000010409 ironing Methods 0.000 description 1
- 239000002655 kraft paper Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000386 microscopy Methods 0.000 description 1
- 230000020477 pH reduction Effects 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000768 polyamine Polymers 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000011122 softwood Substances 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000002166 wet spinning Methods 0.000 description 1
- 239000002023 wood Substances 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
- D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
- D21H13/36—Inorganic fibres or flakes
- D21H13/38—Inorganic fibres or flakes siliceous
- D21H13/40—Inorganic fibres or flakes siliceous vitreous, e.g. mineral wool, glass fibres
-
- 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
- D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
- D21H13/10—Organic non-cellulose fibres
- D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D21H13/22—Condensation polymers of aldehydes or ketones
-
- 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
- D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
- D21H27/08—Filter paper
-
- 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
- D21H5/00—Special paper or cardboard not otherwise provided for
- D21H5/12—Special paper or cardboard not otherwise provided for characterised by the use of special fibrous materials
- D21H5/20—Special paper or cardboard not otherwise provided for characterised by the use of special fibrous materials of organic non-cellulosic fibres too short for spinning, with or without cellulose fibres
Definitions
- This invention relates to fibrous materials and in particular to sheet-like articles containing amino-formaldehyde resin fibres.
- Amino-formaldehyde resin fibres are useful as the fibrous constituents in sheet like articles such as paper where they are generally used in admixture with cellulosic fibres.
- Papers made wholly from amino-formaldehyde resin fibres tend to have little or no strength because generally the fibres exhibit little or no self adhesion. When blended with cellulosic fibres, the latter donate strength to the paper but in many cases it would be desirable to improve the strength still further.
- One way of improving the strength is to employ partially cured (degree of cure 50-90%) amino-formaldehyde resin fibres.
- paper is made from partially cured amino-formaldehyde resin fibres made by employing only mild curing conditions, i.e. weak curing catalysts, low curing temperatures and/or short curing times.
- Partially cured amino-formaldehyde resin fibres can also be made as described in US Patent 4172057 by conducting the reaction of the amino compound with the formaldehyde in the presence of certain carbohydrates.
- the degree of cure of amino-formaldehyde resin fibres is measured by digesting an accurately weighed sample (about 5 g) of the dry fibre in 200 ml of water for 2 hours at 50°C. The undissolved fibre is recovered by filtration, dried at 100°C in air for 2 hours, and then reweighed. The degree of cure is the ratio between the weight of the recovered fibre and the original weight of fibre, and is expressed herein as a percentage.
- amino-formaldehyde resin fibres that have only been partially cured may exhibit some self adhesion and so be used as the sole fibrous component of paper, they suffer from the disadvantages that some of the fibre may be lost during the conventional wet-laid paper production process because of the partial water solubility of the partially cured resin and also that free formaldehyde may be evolved during the paper making process thus constituting a health hazard.
- the processing conditions are such as to cause welding of the amino-formaldehyde resin fibres to each other and/or to other fibrous materials present at at least some of the points where the fibres contact one another.
- Such welding is referred to herein as inter-fibre bonding.
- Inter-fibre bonding can be observed using a microscope: thus if a sample of the article, e.g. paper, is observed using a magnification of x 100 or greater, welds between at least some of the fibres can be seen. It will be appreciated that it is not necessary, in order to obtain useful improvements in strength, that every fibre should be welded to another fibre.
- the degree of inter-fibre bonding should preferably be such that less than 50% by weight of the amino-formaldehyde resin fibres can be removed from the sample as individual fibres without any fibres adhering thereto when the sample is probed with a fine probe.
- inter-fibre bonding is achieved with highly cured amino-formaldehyde resin fibres, i.e. those having a degree of cure above 93%, by heating the sheet material in the presence of water under specified conditions.
- FR-A-2373617 It has been proposed in FR-A-2373617 to dry paper made from certain amino-formaldehyde resin fibres by heating at above 60°C and to improve the cohesion of the paper by heating at over 90°C.
- the fibres are made from an amino-formaldehyde resin that has been modified by the incorporation of certain inorganic oxyacid, e.g. sulphite, radicals.
- certain inorganic oxyacid e.g. sulphite
- Inter-fibre bonded articles made in accordance with the present invention differ from the products of GB-A-1574344 in various respects.
- the incorporation of the UF fragments gives rise to little or no increase in bulk of the paper: the bulk is said to increase by less than 0.1 cm 3 g-' for each 10% by weight of UF fragments incorporated.
- inter-fibre bonded articles containing amino-formaldehyde resin fibres and cellulose fibres exhibit a significant increase in bulk: the bulk increases by at least about 0.15 cm 3 g-' for each 10% by weight of amino-formaldehyde resin fibres incorporated.
- the enhancement in bulk generally becomes more pronounced as the degree of beating of the cellulose pulp increases.
- the amino-formaldehyde resin is in the form of fibres that have been hot cured to a high degree before the shaped article is formed therefrom.
- the present invention provides a process for making a sheet-like article comprising
- inter-fibre bonding in water-sensitive articles can also be assessed by measuring the wet strength of the sample: if inter-fibre bonding has occurred the wet strength of the sample will be increased. It is preferred that the wet strength is increased by at least 25% compared with a similar sample in which no inter-fibre bonding exists.
- the wet strength of a sample in the form of paper may be measured by Tappi Standard Method T456.
- the wet strength measurement and probing may not be indicative of the presence of inter-fibre bonding but such inter-fibre bonding can be detected by microscopy.
- the article contains little or no cellulose fibres, there may be little difference between the wet and dry strengths of the article.
- the article in order to generate inter-fibre bonding, the article is subjected to the action of water at an elevated temperature.
- the fibrous material may be formed into the desired sheet form and then wetted and subjected to the elevated temperature or the article may be formed from an aqueous slurry of the fibrous materials and subjected to the elevated temperature as part of the drying process used to remove the water.
- the paper may be made by a conventional wet-laid process and then subjected to inter-fibre bonding conditions in the drying stages of paper manufacture.
- the conditions required to generate inter-fibre bonding vary with the degree of cure of the amino-formaldehyde resin fibres.
- the degree of cure increases above 93% by weight, the minimum amount of water in the article required to get inter-fibre bonding increases.
- the drying time required decreases.
- the temperature should be at least 80°C and is preferably in the range 90 to 180°C.
- the application of pressure before, or preferably during, the heating step promotes inter-fibre bending.
- the pressure may vary from just sufficient to ensure good contact between adjacent fibres, typically 0.1 to 50 kg cm- 2 (0,01 to 4,9 MPa) or more depending upon the water content and the drying conditions. As the applied pressure increases, less water is required. While the application of pressure greater than that, that is just sufficient to ensure good contact between adjacent fibres is not always necessary, its application enables inter-fibre bonding to be obtained in some borderline cases where, in the absence of applied pressure, no inter-fibre bonding is achieved.
- the time required may vary from about 30 seconds to 10 minutes or more: it will be appreciated that longer times than the minimum required to achieve inter-fibre bonding may be employed.
- the minimum water content required to achieve inter-fibre bonding varies from about 10% by weight of the fibrous material (at low degrees of cure, high temperature and pressure) to over 300% (at low pressures and temperature and high degree of cure). Again it will be appreciated that more water than the minimum required to achieve inter-fibre bonding may be employed. Preferably at least 200% by weight of water is used, based on the dry weight of the fibrous material.
- the amino-formaldehyde resin used to make the amino-formaldehyde resin fibres is a condensate of an amino compound, preferably a polyamine such as urea or melamine, with formaldehyde.
- the amino compound is preferably urea, alone or in admixture with up to 5% by weight of melamine.
- the molar ratio of formaldehyde to amino groups is preferably between 0.6:1 and 1.5:1 particularly between 0.7:1 and 1.3:1.
- the amino-formaldehyde resin fibres may be made by any suitable fibre forming technique such as wet or dry spinning and are preferably formed by a centrifugal spinning process, for example as described in US Patent Specification 4178336, which gives, as is preferred, substantially straight and unbranched fibres.
- the amino-formaldehyde resin fibres preferably have an average length, weighted by length, of between 1 and 10 mm, particularly between 2 and 6 mm. Preferably substantially all the amino-formaldehyde resin fibres have a length within the range 1 to 10 mm.
- the amino-formaldehyde resin fibres preferably have an average diameter between 1 and 20 pm, particularly between 2 and 15 pm, and most particularly between 3 and 10 1 1m. Preferably substantially all the amino-formaldehyde resin fibres have a diameter between 1 and 30 pm.
- the amino-formaldehyde fibres should have a degree of cure of at least 93%, preferably 94 to 99% by weight.
- these degrees of cure are achieved by incorporating a suitable curing catalyst, e.g. ammonium sulphate, ammonium chloride, formic acid, dihydrogen ammonium phosphate, or phosphoric, sulphuric, sulphamic, or hydrochloric acids into the resin prior to spinning into fibres and then heating the fibres after spinning at above 100°C, particularly above 120°C for e.g. up to 3 hours: in general the higher the curing temperature, the shorter the time required.
- 3 hours at 120°C may give a degree of cure of about 94% by weight, only 5 minutes may be required at 180°C to give a degree of cure of about 97%.
- the sheet-like article may be made from the amino-formaldehyde resin fibres as the sole fibrous constituent or may be made from the amino-formaldehyde resin fibres in admixture with other fibrous materials, which may be cellulosic or non-cellulosic.
- the amino-formaldehyde resin fibres should constitute at least 5% by weight of the total fibrous material in the article.
- Particularly useful sheet materials may be made from blends of amino-formaldehyde resin fibres and cellulose fibres containing 5 to 100%, preferably 10 to 50%, by weight of amino-formaldehyde resin fibres.
- Cellulose fibres that may be used include the lignin-free fibres such as cotton linters or chemical wood pulp e.g. paper making pulp made from the raw cellulose by treatment by chemical means such as the well known sulphate or sulphite processes, or lignin-containing fibres such as mechanical, semi-chemical, or thermomechanical wood pulp. Mixtures of lignin-containing and lignin-free cellulose fibres, e.g. mixtures of mechanical and chemical pulps, may be used.
- the cellulose fibres may be lightly beaten or well beaten, depending on the intended use of the article.
- the invention is of particlar merit in the production of sheet like products such as paper and board from fibrous materials comprising amino-formaldehyde resin fibres alone or in admixture with up to 90% by weight, based on the total weight of fibrous material, of cellulose fibres.
- Such products have improved mechanical properties compared to those in which there is no inter-fibre bonding and, in particular, have superior wet strengths.
- inter-fibre bonded amino-aldehyde resin fibre containing papers have superior wet strengths to the 100% cellulose papers which have not been otherwise treated to promote wet strength, e.g. by the inclusion of a wet strength resin binder.
- the use of the amino-resin fibres in admixture with cellulose fibres gives a significant increase in bulk.
- An increase in bulk is generally desirable as it enables less raw materials to be used, with consequent economic advantages, to obtain a paper of given volume. While the bulk of an all-cellulose paper can be increased by reducing the degree of beating of the cellulose, this results in a reduction in paper strength.
- the incorporation of the amino-formaldehyde resin fibres enables an increase in bulk to be achieved without such a large decrease in paper strength.
- the inter-fibre bonded papers of the present invention have improved wet strength compared to papers in which there is no inter-fibre bonding: this renders paper made in accordance with the invention particularly suited to applications such as filter papers. Increased bulk is desirable in such applications as the porosity increases with an increase in bulk.
- the increase in bulk given by the incorporation of the amino-formaldehyde resin fibres becomes greater as the degree of beating of the cellulose fibre increases: thus where the cellulose fibre is lightly beaten, so as to give a paper of high bulk, the increase in bulk may be little more than about but with a more highly beaten cellulose pulp, particularly one giving a paper of bulk below about 2 cm 3 g -1 when made wholly from the cellulose fibre, the increase in bulk is generally at least
- Articles made in accordance with the present invention from a mixture of cellulose fibres and amino-formaldehyde resin fibres are preferably made from fibre mixtures containing 5 to 95, particularly 10 to 50, % by weight of amino-formaldehyde resin fibres and, correspondingly, 95 to 5, particularly 90 to 50%, by weight of cellulose fibres.
- Articles may also be made in accordance with the present invention from fibrous material containing only amino-formaldehyde resin fibres or amino-formaldehyde resin fibres in admixture with non-cellulosic fibres. These mixtures may, if desired, also contain cellulosic fibres.
- the non-cellulosic fibres may be synthetic organic fibres such as polyester, e.g. polyethylene terephthalate, fibres; polyolefin, e.g. polypropylene, fibres; or polyamide fibres; or inorganic fibres such as glass or asbestos fibres.
- the fibrous material contains at least 5% by weight of amino-formaldehyde resin fibres and, correspondingly, up to 95% by weight of the non-cellulosic fibres or mixture of cellulosic and non-cellulosic fibres.
- the amount of non-cellulosic fibres is preferably at least 10% by weight of the total weight of fibres in the article.
- the fibrous material, other than the amino-formaldehyde resin fibres preferably comprises 10 to 100% by weight of non-cellulosic fibres and, correspondingly, 90 to 0% by weight of cellulosic fibres.
- Paper or other sheet like products made in accordance with the present invention from amino-formaldehyde resin fibres alone or from mixtures containing non-cellulosic fibres have a significant strength whether or not they also contain cellulose fibres.
- they may have a burst index (bursting pressure measured according to the TAPPI standard procedure divided by the weight per unit area) of at least 0.2 kPa m2g-1..
- the amino-formaldehyde resin fibres may also be welded to the cellulosic fibres.
- Particularly preferred fibre compositions comprise 10 to 90, especially 20 to 60, % by weight of amino-formaldehyde resin fibres, 10 to 90, especially 20 to 50, % by weight of non-cellulosic fibres, and 0 to 75, especially 10 to 50, % by weight of cellulosic fibres.
- a commercially available aqueous urea/formaldehyde resin having a U:F molar ratio of 1:2 of solids content 67% was diluted with water to a viscosity of 30 poise (3 Pa - s).
- 10%, based on the solids, of an aqueous solution containing 1.6% poly(ethylene oxide) and 6.7% ammonium sulphate was mixed continuously with the resin solution as it was fed to a spinning cup of a centrifugal spinning apparatus.
- the resin was spun by the process described in US Patent Specification 4178336 using a spinning cup of 12.7 cm diameter having 24 rectangular holes and rotating at 7000 rpm.
- the resin was spun at a rate of 100 g min-'.
- the fibres were continuously removed from the spinning apparatus and their cure was continued by heating in air at 150°C for 40 minutes.
- the resultant fibres which had an average diameter of 8.5 pm, had a degree of curing of 94.6%.
- the fibres were cut to a nominal length of 3 mm and dispersed in a standard laboratory pulp disintegrator in water (consistency 1.2%) for 17 minutes.
- Paper handsheets (100% UF resin fibres) were made by the standard procedure using the British Standard Handsheet former with the replacement of the standard pressing step with pressing in a press heated to 110°C. Prior to pressing water was sprayed on to the handsheets and the moisture content was determined by weighing the handsheets before and after pressing.
- Burst Index (burst pressure in kPa divided by the substance in gm- 2 ) was determined according to the standard TAPPI procedure.
- the Breaking Lengths were measured on an Instron tensile tester (table top model) using samples 15 mm wide with a gauge length of 100 mm.
- the crosshead speed was 0.5 cm/min.
- Inter-fibre bonding was assessed microscopically. Its presence is indicated in the following table by a tick.
- Example 1 was repeated using resin fibres cured for 120 minutes at 150°C to give a degree of cure of 96.6%.
- Example 1 was repeated using resin fibres cured for 170 minutes at 150°C to give a degree of cure of 97.9%.
- Example 1 was repeated using resin fibres cured at 150°C for 330 minutes to give a degree of cure of 99.0%.
- Example 1 was repeated using resin fibres cured for 30 minutes at 150°C to give a degree of cure of 96.4%. In each case the pressing time was 3 minutes at 110°C.
- Example 1 was repeated using fibres cured for 30 minutes at 150°C to give a degree of cure of 95.9%.
- the moist sheets were pressed at a pressure of about 0.1 kg cm- 2 for varying times at various temperatures.
- paper handsheets were made from 80% birch sulphate pulp and 20% urea-formaldehyde resin fibres similar to those used in Example 1. Some of the handsheets were wetted and dried under inter-fibre bonding inducing conditions and the wet breaking length was measured.
- a similar handsheet made wholly from the birch sulphate pulp had wet breaking length of 0.09 km.
- Example 7 was repeated but using a 50/50 mixture of the birch sulphate pulp and the urea- formaldehyde resin fibres.
- Papers were made on a pilot paper making machine from mixtures of lightly beaten bleached hardwood sulphate cellulose pulp and urea-formaldehyde resin fibres made by the procedure described in Example 1 and having a degree of cure of 94.6%.
- the paper was dried under light pressure against cylinders heated to about 100°C. The drying time and moisture content were sufficient to give inter-fibre bonding.
- Paper was also made and dried under the same conditions from the lightly beaten cellulose pulp alone.
- the tensile strengths (wet and dry) in the transverse direction of the paper, i.e. at right angles to the machine direction, and the wet burst index was measured and are quoted in the table as a percentage of the corresponding properties of the all-cellulose paper. It is seen that the bulk increases by over 0.017 cm 3 g -1 for each percent of urea-formaldehyde fibres incorporated.
- Example 1 was repeated using urea-formaldehyde resin fibres of average diameter 9 11m and 94.9% degree of cure, in admixture with glass or polyethylene terephthalate (PET) fibres, and also, in some cases with softwood sulphate cellulose pulp.
- PET polyethylene terephthalate
- the glass fibres had a mean diameter of 20 ⁇ m while the PETfibres were 1.5 denier, drawn, uncrimped fibres that had been washed in warm water to remove any spin finish from their surfaces.
- the glass, PET, and urea-formaldehyde fibres were cut to provide a length distribution between 1 and 5 mm by passing the fibres twice through a paper shredding machine with the cutters spaced at a nominal 3 mm.
- the sheets were couched from the wire of the sheet former, placed on a non-stick plate, weighed, sprayed evenly with a little deionised water, reweighed and then pressed on each side for 30 seconds using a domestic ironing press at 170°C giving an applied pressure of about 0.1 kg cm- 2 .
- the weight of the dried paper was determined.
- the solids content of each sheet entering the press was thus determined, and so the moisture content as a percentage of the total fibre content was calculated.
- Example 6 of UK Patent Specification 1573115 the production of paper from a mixture of urea-formaldehyde resin fibres and cellulose pulp on a Fourdrinier paper making machine is described. Examination of a sample of the paper produced in that Example revealed no inter-fibre bonding.
- Urea-formaldehyde resin fibres made by the procedure described in Example 1 and having a degree of cure of 94% were mixed, in various proportions with a beaten cellulose pulp and made into handsheets by the British Standard method (which involves air drying at room temperature and does not promote inter-fibre bonding).
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Paper (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
- Materials For Medical Uses (AREA)
Description
- This invention relates to fibrous materials and in particular to sheet-like articles containing amino-formaldehyde resin fibres.
- Amino-formaldehyde resin fibres are useful as the fibrous constituents in sheet like articles such as paper where they are generally used in admixture with cellulosic fibres.
- Papers made wholly from amino-formaldehyde resin fibres tend to have little or no strength because generally the fibres exhibit little or no self adhesion. When blended with cellulosic fibres, the latter donate strength to the paper but in many cases it would be desirable to improve the strength still further.
- One way of improving the strength is to employ partially cured (degree of cure 50-90%) amino-formaldehyde resin fibres. Thus in EP-A-14026, paper is made from partially cured amino-formaldehyde resin fibres made by employing only mild curing conditions, i.e. weak curing catalysts, low curing temperatures and/or short curing times. Partially cured amino-formaldehyde resin fibres can also be made as described in US Patent 4172057 by conducting the reaction of the amino compound with the formaldehyde in the presence of certain carbohydrates.
- The degree of cure of amino-formaldehyde resin fibres is measured by digesting an accurately weighed sample (about 5 g) of the dry fibre in 200 ml of water for 2 hours at 50°C. The undissolved fibre is recovered by filtration, dried at 100°C in air for 2 hours, and then reweighed. The degree of cure is the ratio between the weight of the recovered fibre and the original weight of fibre, and is expressed herein as a percentage.
- While amino-formaldehyde resin fibres that have only been partially cured may exhibit some self adhesion and so be used as the sole fibrous component of paper, they suffer from the disadvantages that some of the fibre may be lost during the conventional wet-laid paper production process because of the partial water solubility of the partially cured resin and also that free formaldehyde may be evolved during the paper making process thus constituting a health hazard.
- It has now found that, under certain conditions, articles, e.g. paper, of improved strength, containing amino-formaldehyde resin fibres having a higher degree of cure can be made.
- In the present invention, the processing conditions are such as to cause welding of the amino-formaldehyde resin fibres to each other and/or to other fibrous materials present at at least some of the points where the fibres contact one another. Such welding is referred to herein as inter-fibre bonding. Inter-fibre bonding can be observed using a microscope: thus if a sample of the article, e.g. paper, is observed using a magnification of x 100 or greater, welds between at least some of the fibres can be seen. It will be appreciated that it is not necessary, in order to obtain useful improvements in strength, that every fibre should be welded to another fibre. However the degree of inter-fibre bonding should preferably be such that less than 50% by weight of the amino-formaldehyde resin fibres can be removed from the sample as individual fibres without any fibres adhering thereto when the sample is probed with a fine probe. In the present invention inter-fibre bonding is achieved with highly cured amino-formaldehyde resin fibres, i.e. those having a degree of cure above 93%, by heating the sheet material in the presence of water under specified conditions.
- It has been proposed in FR-A-2373617 to dry paper made from certain amino-formaldehyde resin fibres by heating at above 60°C and to improve the cohesion of the paper by heating at over 90°C. The fibres are made from an amino-formaldehyde resin that has been modified by the incorporation of certain inorganic oxyacid, e.g. sulphite, radicals. However the inorganic oxyacid radicals incorporated into the resin reduce the degree of cure of the fibres and so the procedure of FR-A-2373617 suffers from the same disadvantages as the procedures of the aforementioned EP-A-14026 and US-A-4172057.
- It has been proposed in GB-A-1574344 to make paper from a mixture of cellulose pulp and urea-formaldehyde (UF) resin fragments, particularly fragments of a UF foam, that have been partially cured by acidification at a temperature below 60°C. After forming the cellulose pulp/UF fragments mixture into sheet form, the latter is heated at above 80°C to effect further curing of the UF resin. It is said that this process gives a continuous chemically bonded network in the paper.
- Inter-fibre bonded articles made in accordance with the present invention differ from the products of GB-A-1574344 in various respects.
- In the process of GB-A-1574344 the use of a cellulose pulp is essential and it is postulated that a chemical bond is formed between the UF fragments and the cellulose: it is indicated that papers made from non-cellulosic fibres and the fragments have insignificant strength. In contrast inter-fibre bonded articles of significant strength can be made in accordance with the present invention using amino-formaldehyde resin fibres alone or in admixture with non-cellulosic fibrous materials.
- Furthermore it is indicated in GB-A-1574344 that the incorporation of the UF fragments gives rise to little or no increase in bulk of the paper: the bulk is said to increase by less than 0.1 cm3g-' for each 10% by weight of UF fragments incorporated. In contrast thereto inter-fibre bonded articles containing amino-formaldehyde resin fibres and cellulose fibres exhibit a significant increase in bulk: the bulk increases by at least about 0.15 cm3g-' for each 10% by weight of amino-formaldehyde resin fibres incorporated. The enhancement in bulk generally becomes more pronounced as the degree of beating of the cellulose pulp increases.
- In contrast to the process of GB-A-1574344, in the present invention the amino-formaldehyde resin is in the form of fibres that have been hot cured to a high degree before the shaped article is formed therefrom.
- Accordingly the present invention provides a process for making a sheet-like article comprising
- (i) forming a solution of an amino-formaldehyde resin free of bound inorganic oxyacid radicals and a curing catalyst therefor into fibres,
- (ii) curing said fibres by heating them at above 100°C until the degree of cure (as assessed by the procedure hereinbefore described) is above 93%,
- (iii) forming an aqueous pulp by dispersing fibrous material in water, said fibrous material containing at least 5% by weight of said cured amino-formaldehyde resin fibres,
- (iv) forming a sheet-like article from said pulp, and
- (v) promiting inter-fibre bonding by heating said article at a sufficiently high temperature above 80°C, for sufficient time, and in the presence of a sufficient amount of water above 10% by weight of the total weight of fibrous material present, with the application of pressure, before or during said heating, at least sufficient to cause contact between adjacent fibres, so as to cause at least some of the amino-formaldehyde resin fibres to weld to one another and/or to other fibrous material present at at least some of the points where the fibres touch one another.
- While applicants do not wish to be bound by the following theory, it is thought that, in the process of the present invention, at least some of the highly cured amino-formaldehyde resin fibres undergo slight hydrolysis at their surfaces thus rendering them somewhat tacky under the prevailing conditions of temperature and moisture. Where such a tackified fibre contacts, e.g. at a point where fibres cross, another fibre (whether or not the other fibre is another tackified amino-formaldehyde resin fibre) fusion or welding at the intersection occurs. As no tackiness of the fibres is however detected in the final product it is thought that dehydration and recondensation of the tackified fibre surfaces occurs as the heating and drying is continued.
- The existence of inter-fibre bonding in water-sensitive articles, e.g. paper containing some cellulosic fibres, can also be assessed by measuring the wet strength of the sample: if inter-fibre bonding has occurred the wet strength of the sample will be increased. It is preferred that the wet strength is increased by at least 25% compared with a similar sample in which no inter-fibre bonding exists. The wet strength of a sample in the form of paper may be measured by Tappi Standard Method T456.
- It will be appreciated that where a binder is present in the article the wet strength measurement and probing may not be indicative of the presence of inter-fibre bonding but such inter-fibre bonding can be detected by microscopy.
- Where the article contains little or no cellulose fibres, there may be little difference between the wet and dry strengths of the article.
- In the process of the invention in order to generate inter-fibre bonding, the article is subjected to the action of water at an elevated temperature.
- The fibrous material may be formed into the desired sheet form and then wetted and subjected to the elevated temperature or the article may be formed from an aqueous slurry of the fibrous materials and subjected to the elevated temperature as part of the drying process used to remove the water. Thus in the production of paper-like sheet articles, the paper may be made by a conventional wet-laid process and then subjected to inter-fibre bonding conditions in the drying stages of paper manufacture.
- The conditions required to generate inter-fibre bonding vary with the degree of cure of the amino-formaldehyde resin fibres. Thus as the degree of cure increases above 93% by weight, the minimum amount of water in the article required to get inter-fibre bonding increases. As the temperature increases the drying time required decreases.
- The temperature should be at least 80°C and is preferably in the range 90 to 180°C. The application of pressure before, or preferably during, the heating step promotes inter-fibre bending. The pressure may vary from just sufficient to ensure good contact between adjacent fibres, typically 0.1 to 50 kg cm-2 (0,01 to 4,9 MPa) or more depending upon the water content and the drying conditions. As the applied pressure increases, less water is required. While the application of pressure greater than that, that is just sufficient to ensure good contact between adjacent fibres is not always necessary, its application enables inter-fibre bonding to be obtained in some borderline cases where, in the absence of applied pressure, no inter-fibre bonding is achieved.
- The time required may vary from about 30 seconds to 10 minutes or more: it will be appreciated that longer times than the minimum required to achieve inter-fibre bonding may be employed.
- The minimum water content required to achieve inter-fibre bonding varies from about 10% by weight of the fibrous material (at low degrees of cure, high temperature and pressure) to over 300% (at low pressures and temperature and high degree of cure). Again it will be appreciated that more water than the minimum required to achieve inter-fibre bonding may be employed. Preferably at least 200% by weight of water is used, based on the dry weight of the fibrous material.
- Simple experimentation will enable conditions where inter-fibre bonding results to be determined.
- The amino-formaldehyde resin used to make the amino-formaldehyde resin fibres is a condensate of an amino compound, preferably a polyamine such as urea or melamine, with formaldehyde. The amino compound is preferably urea, alone or in admixture with up to 5% by weight of melamine. The molar ratio of formaldehyde to amino groups is preferably between 0.6:1 and 1.5:1 particularly between 0.7:1 and 1.3:1.
- The amino-formaldehyde resin fibres may be made by any suitable fibre forming technique such as wet or dry spinning and are preferably formed by a centrifugal spinning process, for example as described in US Patent Specification 4178336, which gives, as is preferred, substantially straight and unbranched fibres.
- The amino-formaldehyde resin fibres preferably have an average length, weighted by length, of between 1 and 10 mm, particularly between 2 and 6 mm. Preferably substantially all the amino-formaldehyde resin fibres have a length within the range 1 to 10 mm.
- The amino-formaldehyde resin fibres preferably have an average diameter between 1 and 20 pm, particularly between 2 and 15 pm, and most particularly between 3 and 10 11m. Preferably substantially all the amino-formaldehyde resin fibres have a diameter between 1 and 30 pm. The amino-formaldehyde resin fibres preferably have an average strength of at least 50 Mnm-2 (which corresponds approximately to 33 Nmg-1), particularly at least 100 MNm-2 (=67 Nmg-1).
- The amino-formaldehyde fibres should have a degree of cure of at least 93%, preferably 94 to 99% by weight. In the process of the present invention, these degrees of cure are achieved by incorporating a suitable curing catalyst, e.g. ammonium sulphate, ammonium chloride, formic acid, dihydrogen ammonium phosphate, or phosphoric, sulphuric, sulphamic, or hydrochloric acids into the resin prior to spinning into fibres and then heating the fibres after spinning at above 100°C, particularly above 120°C for e.g. up to 3 hours: in general the higher the curing temperature, the shorter the time required. Thus while 3 hours at 120°C may give a degree of cure of about 94% by weight, only 5 minutes may be required at 180°C to give a degree of cure of about 97%.
- The sheet-like article may be made from the amino-formaldehyde resin fibres as the sole fibrous constituent or may be made from the amino-formaldehyde resin fibres in admixture with other fibrous materials, which may be cellulosic or non-cellulosic. The amino-formaldehyde resin fibres should constitute at least 5% by weight of the total fibrous material in the article.
- Particularly useful sheet materials, e.g. paper and board, may be made from blends of amino-formaldehyde resin fibres and cellulose fibres containing 5 to 100%, preferably 10 to 50%, by weight of amino-formaldehyde resin fibres. Cellulose fibres that may be used include the lignin-free fibres such as cotton linters or chemical wood pulp e.g. paper making pulp made from the raw cellulose by treatment by chemical means such as the well known sulphate or sulphite processes, or lignin-containing fibres such as mechanical, semi-chemical, or thermomechanical wood pulp. Mixtures of lignin-containing and lignin-free cellulose fibres, e.g. mixtures of mechanical and chemical pulps, may be used.
- The cellulose fibres may be lightly beaten or well beaten, depending on the intended use of the article.
- The invention is of particlar merit in the production of sheet like products such as paper and board from fibrous materials comprising amino-formaldehyde resin fibres alone or in admixture with up to 90% by weight, based on the total weight of fibrous material, of cellulose fibres. Such products have improved mechanical properties compared to those in which there is no inter-fibre bonding and, in particular, have superior wet strengths. Thus inter-fibre bonded amino-aldehyde resin fibre containing papers have superior wet strengths to the 100% cellulose papers which have not been otherwise treated to promote wet strength, e.g. by the inclusion of a wet strength resin binder.
- As mentioned hereinbefore, in contrast to the papers described in GB-A-1574344, the use of the amino-resin fibres in admixture with cellulose fibres gives a significant increase in bulk. An increase in bulk is generally desirable as it enables less raw materials to be used, with consequent economic advantages, to obtain a paper of given volume. While the bulk of an all-cellulose paper can be increased by reducing the degree of beating of the cellulose, this results in a reduction in paper strength. The incorporation of the amino-formaldehyde resin fibres enables an increase in bulk to be achieved without such a large decrease in paper strength.
- As mentioned hereinbefore, the inter-fibre bonded papers of the present invention have improved wet strength compared to papers in which there is no inter-fibre bonding: this renders paper made in accordance with the invention particularly suited to applications such as filter papers. Increased bulk is desirable in such applications as the porosity increases with an increase in bulk.
- Articles made in accordance with the present invention from a mixture of amino-formaldehyde resin fibres and cellulose fibres, i.e. cellulose pulp, having a bulk of at least
- Articles made in accordance with the present invention from a mixture of cellulose fibres and amino-formaldehyde resin fibres are preferably made from fibre mixtures containing 5 to 95, particularly 10 to 50, % by weight of amino-formaldehyde resin fibres and, correspondingly, 95 to 5, particularly 90 to 50%, by weight of cellulose fibres.
- Articles may also be made in accordance with the present invention from fibrous material containing only amino-formaldehyde resin fibres or amino-formaldehyde resin fibres in admixture with non-cellulosic fibres. These mixtures may, if desired, also contain cellulosic fibres. The non-cellulosic fibres may be synthetic organic fibres such as polyester, e.g. polyethylene terephthalate, fibres; polyolefin, e.g. polypropylene, fibres; or polyamide fibres; or inorganic fibres such as glass or asbestos fibres.
- Where non-cellulosic fibres, or a mixture of cellulosic and non-cellulosic fibres are employed, the fibrous material contains at least 5% by weight of amino-formaldehyde resin fibres and, correspondingly, up to 95% by weight of the non-cellulosic fibres or mixture of cellulosic and non-cellulosic fibres. The amount of non-cellulosic fibres is preferably at least 10% by weight of the total weight of fibres in the article. The fibrous material, other than the amino-formaldehyde resin fibres, preferably comprises 10 to 100% by weight of non-cellulosic fibres and, correspondingly, 90 to 0% by weight of cellulosic fibres.
- Paper or other sheet like products made in accordance with the present invention from amino-formaldehyde resin fibres alone or from mixtures containing non-cellulosic fibres, have a significant strength whether or not they also contain cellulose fibres. Thus they may have a burst index (bursting pressure measured according to the TAPPI standard procedure divided by the weight per unit area) of at least 0.2 kPa m2g-1..
- Where the article contains cellulose fibres in addition to the non-cellulosic fibres, the amino-formaldehyde resin fibres may also be welded to the cellulosic fibres.
- Particularly preferred fibre compositions comprise 10 to 90, especially 20 to 60, % by weight of amino-formaldehyde resin fibres, 10 to 90, especially 20 to 50, % by weight of non-cellulosic fibres, and 0 to 75, especially 10 to 50, % by weight of cellulosic fibres.
- The invention is illustrated by the following examples in which all percentages are expressed by weight.
- A commercially available aqueous urea/formaldehyde resin having a U:F molar ratio of 1:2 of solids content 67% was diluted with water to a viscosity of 30 poise (3 Pa - s). 10%, based on the solids, of an aqueous solution containing 1.6% poly(ethylene oxide) and 6.7% ammonium sulphate was mixed continuously with the resin solution as it was fed to a spinning cup of a centrifugal spinning apparatus. The resin was spun by the process described in US Patent Specification 4178336 using a spinning cup of 12.7 cm diameter having 24 rectangular holes and rotating at 7000 rpm.
- Air at 180°C was blown into the spinning chamber to dry the fibres, to transport them from the spinning cup and to effect some curing. The resin was spun at a rate of 100 g min-'. The fibres were continuously removed from the spinning apparatus and their cure was continued by heating in air at 150°C for 40 minutes.
- The resultant fibres, which had an average diameter of 8.5 pm, had a degree of curing of 94.6%.
- The fibres were cut to a nominal length of 3 mm and dispersed in a standard laboratory pulp disintegrator in water (consistency 1.2%) for 17 minutes.
- Paper handsheets (100% UF resin fibres) were made by the standard procedure using the British Standard Handsheet former with the replacement of the standard pressing step with pressing in a press heated to 110°C. Prior to pressing water was sprayed on to the handsheets and the moisture content was determined by weighing the handsheets before and after pressing.
- After pressing the Burst Index, and Breaking Lengths of the papers were determined.
- Burst Index (burst pressure in kPa divided by the substance in gm-2) was determined according to the standard TAPPI procedure. The Breaking Lengths were measured on an Instron tensile tester (table top model) using samples 15 mm wide with a gauge length of 100 mm. The crosshead speed was 0.5 cm/min.
-
-
-
-
-
-
- The papers of Examples 1 to 6 that exhibited inter-fibre bonding maintained their integrity when immersed in water and gently agitated: those in which there was no inter-fibre bonding did not.
- To demonstrate the improvement obtained in the wet strength of papers made from mixtures of urea-formaldehyde resin fibres and cellulose fibres by the present invention, paper handsheets were made from 80% birch sulphate pulp and 20% urea-formaldehyde resin fibres similar to those used in Example 1. Some of the handsheets were wetted and dried under inter-fibre bonding inducing conditions and the wet breaking length was measured.
-
- A similar handsheet made wholly from the birch sulphate pulp had wet breaking length of 0.09 km.
-
- Papers were made on a pilot paper making machine from mixtures of lightly beaten bleached hardwood sulphate cellulose pulp and urea-formaldehyde resin fibres made by the procedure described in Example 1 and having a degree of cure of 94.6%. The paper was dried under light pressure against cylinders heated to about 100°C. The drying time and moisture content were sufficient to give inter-fibre bonding.
- Paper was also made and dried under the same conditions from the lightly beaten cellulose pulp alone. The tensile strengths (wet and dry) in the transverse direction of the paper, i.e. at right angles to the machine direction, and the wet burst index was measured and are quoted in the table as a percentage of the corresponding properties of the all-cellulose paper.
- Example 1 was repeated using urea-formaldehyde resin fibres of average diameter 9 11m and 94.9% degree of cure, in admixture with glass or polyethylene terephthalate (PET) fibres, and also, in some cases with softwood sulphate cellulose pulp.
- The glass fibres had a mean diameter of 20 µm while the PETfibres were 1.5 denier, drawn, uncrimped fibres that had been washed in warm water to remove any spin finish from their surfaces.
- The glass, PET, and urea-formaldehyde fibres were cut to provide a length distribution between 1 and 5 mm by passing the fibres twice through a paper shredding machine with the cutters spaced at a nominal 3 mm.
- To promote inter-fibre bonding the sheets were couched from the wire of the sheet former, placed on a non-stick plate, weighed, sprayed evenly with a little deionised water, reweighed and then pressed on each side for 30 seconds using a domestic ironing press at 170°C giving an applied pressure of about 0.1 kg cm-2. The weight of the dried paper was determined. The solids content of each sheet entering the press was thus determined, and so the moisture content as a percentage of the total fibre content was calculated.
- Two sheets were prepared for each variation in the furnish and the Burst Index was measured at four locations on each sheet, and the average Burst Index was determined.
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- In Example 6 of UK Patent Specification 1573115 the production of paper from a mixture of urea-formaldehyde resin fibres and cellulose pulp on a Fourdrinier paper making machine is described. Examination of a sample of the paper produced in that Example revealed no inter-fibre bonding.
- Urea-formaldehyde resin fibres made by the procedure described in Example 1 and having a degree of cure of 94% were mixed, in various proportions with a beaten cellulose pulp and made into handsheets by the British Standard method (which involves air drying at room temperature and does not promote inter-fibre bonding).
- Similar sheets were also made but inter-fibre bonding induced by drying the sheets under light pressure against a cylinder heated to about 100°C.
-
- It is seen that inter-fibre bonding gives a significant enhancement in the burst index.
Claims (8)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT81301359T ATE13702T1 (en) | 1980-04-16 | 1981-03-27 | FIBER MATERIALS. |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8012488 | 1980-04-16 | ||
GB8012488 | 1980-04-16 | ||
GB8024696 | 1980-07-29 | ||
GB8024696 | 1980-07-29 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0038136A1 EP0038136A1 (en) | 1981-10-21 |
EP0038136B1 true EP0038136B1 (en) | 1985-06-05 |
Family
ID=26275193
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP81301359A Expired EP0038136B1 (en) | 1980-04-16 | 1981-03-27 | Fibrous materials |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0038136B1 (en) |
AU (1) | AU540107B2 (en) |
DE (1) | DE3170814D1 (en) |
FI (1) | FI66946C (en) |
NO (1) | NO811169L (en) |
NZ (1) | NZ196721A (en) |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3101294A (en) * | 1959-12-17 | 1963-08-20 | Du Pont | Process for forming a web of synthetic fibers |
GB1573114A (en) * | 1976-12-08 | 1980-08-13 | Ici Ltd | Paper |
-
1981
- 1981-03-27 DE DE8181301359T patent/DE3170814D1/en not_active Expired
- 1981-03-27 EP EP81301359A patent/EP0038136B1/en not_active Expired
- 1981-04-02 NZ NZ196721A patent/NZ196721A/en unknown
- 1981-04-03 AU AU69086/81A patent/AU540107B2/en not_active Ceased
- 1981-04-06 NO NO811169A patent/NO811169L/en unknown
- 1981-04-15 FI FI811181A patent/FI66946C/en not_active IP Right Cessation
Also Published As
Publication number | Publication date |
---|---|
EP0038136A1 (en) | 1981-10-21 |
FI66946B (en) | 1984-08-31 |
AU6908681A (en) | 1981-10-22 |
FI811181L (en) | 1981-10-17 |
DE3170814D1 (en) | 1985-07-11 |
AU540107B2 (en) | 1984-11-01 |
FI66946C (en) | 1984-12-10 |
NZ196721A (en) | 1983-11-18 |
NO811169L (en) | 1981-10-19 |
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