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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/18—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only forming new compounds in situ, e.g. within the pulp or paper, by chemical reaction with itself, or other added substances, e.g. by grafting on the fibres
  • D21H17/19—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only forming new compounds in situ, e.g. within the pulp or paper, by chemical reaction with itself, or other added substances, e.g. by grafting on the fibres by reactions only involving carbon-to-carbon unsaturated bonds
• • 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
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/04—Physical treatment, e.g. heating, irradiating
  • D21H25/06—Physical treatment, e.g. heating, irradiating of impregnated or coated 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
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/08—Filter paper

Definitions

• the invention relates to a method for producing impregnated papers, in particular porous papers for further processing into filters for internal combustion engines and the like.
• Filters are required for various technical purposes, which on the one hand should have a high retention capacity and on the other hand are resistant to the medium to be filtered.
• filter papers with special impregnation are used.
• the structure of this filter paper is such that it allows air to pass through opposed to innumerable pores only slight resistance, but on the other hand only allows the smallest and therefore harmless dust particles to pass through because of the fineness of the pores.
• Filters with the same structure are also used as oil filters in internal combustion engines.
• the filters were manufactured from porous paper webs that were impregnated with uncrosslinked phenolic resins.
• the crosslinking or curing of the phenolic resins takes place after soaking at an elevated temperature.
• This method of preparation was generally very expensive, since the curing of the resins at temperatures of the order of 16 0 ° C to 18 0 ° C was required and at considerable residence times of curing units 3o to 5o meters in length.
• the phenolic resin vapors released during the curing process entail considerable environmental pollution.
• the environmental protection problems essentially lie in the fact that the alcohol-soluble phenolic resins or phenolic resin vapors can reach the exhaust air or waste water.
• the process was further complicated by the fact that the curing process could not be carried out in one process step, but had to be interrupted during the filter manufacture.
• the hardening or condensation process was interrupted to allow the paper to be folded or pleated.
• the final condensation was only carried out after the folding, in which there are some tears in the paper at the folded edges. This final condensation itself is therefore necessary so that the paper no longer contains any volatile constituents that can migrate into the medium to be filtered.
• the precondensation is carried out so far that the paper or the resin contained therein no longer sticks to one another and thereby be becomes workable.
• the invention is therefore based on the object of specifying a process for the production of impregnated papers which can be used in particular for filters of internal combustion engines and which allow a very economical production of these filters with high quality.
• the process should be economical, avoid environmental pollution and be carried out with the lowest possible system outlay.
• the object is achieved in that the paper web is subjected to at least one impregnation with an aqueous emulsion in the paper machine: a resin and / or monomer curable by high-energy radiation and that the impregnated paper web is then subjected to electronic radiation curing.
• the paper machine which is anyway necessary for producing the paper web, and an installation for electronic radiation curing, the paper machine being provided at a suitable point with a device which permits impregnation of the paper web.
• the impregnation can be done through a commission, e.g. B. a size press can be performed.
• An aqueous emulsion of a resin curable under electronic radiation is preferably used as the impregnating agent.
• the resin to be used in the process according to the invention is added to the paper web in the paper machine in the form of an aqueous emulsion or solution.
• Resins and / or monomers based on acrylic acid and / or methacrylic acid esters with polyols are used.
• the emulsion itself has a resin proportion of 15 to 7 0 wt .-%.
• the use of an emulsion has the advantage that the resin particles can penetrate the paper very well.
• the resin is added to the paper in an amount of 10 to 30% by weight, preferably 20% by weight.
• the distribution of the resin should be even, so that the filter effect is even across the entire filter.
• the preferred resin content in the paper for the filters is 20% by weight.
• the resin content should be as low as possible.
• the resin content can vary. At high strengths, a higher resin content is introduced to 3 0%, while at low strengths already a resin content of about 1o% until sufficient.
• the resin components are fully cross-linked in the electron beam curing system. This is very important, as any non-cross-linked portions, as noted above, can be absorbed by the filtered medium.
• the content of soluble components in the finished filter should be as low as possible.
• the production according to the invention has the advantage that the resins used are not soluble in alcohols.
• the alcohols can lead to the dissolution of conventional resins.
• alcohol fuels can also remove uncondensed phenolic resin from the filters.
• the paper web is made from a predominantly long-fiber cellulose.
• the proportion of long-fiber cellulose is preferably more than 9 0%. It is also favorable to use a cotton cellulose as cellulose.
• the cellulose used has a low freeness of 13 to 15 Schopper regulators. Due to the low degree of grinding of the cellulose used, which, as already mentioned above, is preferably cotton cellulose, a so-called cotton linter, the paper web and also the subsequent filter are given high strength. In order to increase the strength of the paper web, customary so-called wet-solid materials can also be added to the pulp.
• Resin pickup by the paper web is preferred Controlled by the initial moisture of the paper web when entering the size press. The higher this initial moisture content, the lower the resin absorption. Furthermore, the speed of the paper web is used to control the resin uptake. At higher paper web speeds, smaller amounts of resin are taken up.
• the paper web After radiation curing, the paper web is cut into individual sheets corresponding to the filter sizes. These sheets are folded, provided with an adhesive line on one edge and glued together. It should be noted that the porosity of the filter papers produced in this way is very remarkable. The less resin is used, the better the filter effect. However, the burst pressure is all the less. Depending on the purpose for which the filter is used, more or less resin can consequently be added to the paper web, i. that is, the strength of the paper web can be increased more or less.
• the paper webs produced according to the invention can be subjected to folding without damage occurring in the paper web at the folded edges. Consequently, the folded air filters required for internal combustion engines can be produced particularly well from the paper web.
• the filters produced in this way also have a number of other advantages; so the filters can withstand high pressure.
• a burst pressure of 2.2 to 2.5 bar is required.
• the lower limit is generally considered to be 1.8 bar.
• Filters manufactured using the new process have burst pressures that are significantly higher.
• the filters previously produced from phenol generally had a brown color
• the filters produced by the process according to the invention have no coloration due to the process, i. that is, the filters are white. This is very cheap, for example, if the color alone is used to determine whether the filter was already in use or not.
• aqueous emulsions of monomers or resins which can be hardened by electron radiation or other high-energy radiation are used as impregnating agents.
• Particularly suitable monomers are polyacrylated and / or polymethacrylated polyols, polyacrylated polyols being preferred because of the higher reaction rate.
• Suitable resins for preparing the emulsions are, for example, the resins and / or monomers proposed in the aforementioned DE-PS (patent application P 29 33 998.8).
• hydroxyl groups of the polyols mentioned can be wholly or partially esterified by acrylic acid and / or methacrylic acid.
• Specific examples of the present invention usable monomers are trimethylolpropane triacrylate, hexanediol diacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, hexane-1, 6-diol diacrylate, Diäthylenglykoldiacrylat, Triäthylenglykoldiacrylat, Tetraäthylen- - glycol diacrylate, tripropylene glycol diacrylate, 2-ethyl acrylate Hydrox-, 2-Hydroxypropoylacrylat, Hexandiolmonoacrylate and Butandiolmonoacrylate and the corresponding Methacrylates or mixed acrylate methacrylates.
• the monomers can be used alone or in a mixture, if appropriate with high or low molecular weight prepolymers.
• Particularly suitable monomers are pentaerythritol triacrylate or pentaerythritol acrylate mixtures having a average degree of esterification from 3 to 3.3 and having a viscosity of 6 00 - 12oo mPa.s (measured at 2 0 0 C with a Brookfield viscometer, Type RVT).
• High or low molecular weight resins or oligomers are suitable as resins.
• these are soluble polyurethane acrylates formed from the aforementioned hydroxy-functional acrylate monomers.
• the molecular weight is such resins or oligomers in the range of 8 00 - 8000 and their viscosities going from looo - 5 0000 mPa.s.
• the content of acrylic and / or methacrylic unsaturated monomer units is, for example, 2-6 per molecule.
• Resins of this type are produced by customary procedures, for example as described in DE-OS 25 3 0 896 and DE-OS 25 42 314. For example, a polyol is reacted with a diisocyanate. The content of free NCO groups reached is then saturated with hydroxy-functional acrylate or methacrylate monomers.
• the person skilled in the art can select amounts and reaction conditions such that the desired molecular weights and the desired content of acrylic and / or methacrylic unsaturated monomer units are achieved.
• the viscosities can be varied, for example, by appropriate dilution of the resins with monomers.
• the acrylic or methacrylic, unsaturated monomers and / or oligomers explained above with reference to examples are processed into oil-in-water (0 / W) emulsions using emulsifiers.
• the total solids content of these emulsions which consists predominantly of the monomer and / or oligomers together with the emulsifiers, is generally from about 15 to 7o wt .-%, preferably from 2o to 6 wt .-% and the 0 especially around 40% by weight, based on the finished emulsion.
• the particle size of the resulting emulsion is ⁇ 1 / um and preferably o.4 to o.6 / um. This particle size is achieved by conventional measures, such as the selection of suitable emulsifiers and emulsification conditions.
• Suitable emulsifiers for the emulsions used according to the invention are in principle nonionic emulsifiers, anionic and cationic emulsifiers, alone or in a mixture with one another.
• emulsions were produced with a particle size of ⁇ 1 / um and a heat storage stability of 2 to 6 months at temperatures of 3o to 60 ° C.
• the amount of emulsifier used depends on the monomers and / or oligomers used and on the emulsifying conditions. Generally one needs from. the emulsifiers or their mixtures 1 to 7 wt .-%, preferably 1 to 3 wt .-%, calculated on the inner phase or the total solids content of the O / W emulsion.
• Amounts of o, o2 - 0.4% by weight have proven useful, but particularly amounts of o, 1 - 0.3% by weight, based on the total batch, have proven effective.
• the amount used is preferably 0.05-0.5% by weight, based on the total batch, in particular 0.1-0.4% by weight.
• the impregnating resin emulsion used according to the invention can be prepared by any process which is suitable for the preparation of oil-in-water emulsions and which leads to the desired particle size.
• the above-mentioned monomers and / or oligomers can be converted into an O / W emulsion as follows.
• the aqueous emulsions used according to the invention have a solids content (monomer and / or oligomer plus emulsifier and further additives or auxiliaries) of about 15 to 70% by weight.
• concentration of the monomer and / or oligomer or resin ultimately depends on the desired degree of coverage of the substrate with the monomer, oligomer or resin.
• the nonwoven or paper materials impregnated according to the invention are cured by high-energy radiation, as mentioned at the beginning.
• the unsaturated acrylate resin is cured by radical chain polymerization, which leads to chain growth with a high three-dimensional degree of branching.
• Electron or B radiation is preferably used.
• the radiation can be generated by conventional electron sources.
• one or more stage electron accelerators are used, for example the electron accelerators described in DE-PS (patent application P 29 33 998.8 of Wikolin Polymer Chemie GmbH and Otto Dürr Anlagenbau GmbH).
• the paper webs impregnated according to the invention are optionally passed under an inert gas, such as nitrogen, past a window from which the electron radiation emerges.
• an inert gas such as nitrogen
• the acceleration voltages of the single or multi-stage electron accelerators used are, for example , at about 15o to 5 o 0 kV, the irradiation dose is, for example about 0.1 to about 16 Mrad.
• An example of an emulsifiable monomer is: pentacrythritol triacrylate (average degree of esterification 3.3, viscosity 6 00 - 9 00 m p as)
• the flask is equipped with a condenser (water-cooled), a stirrer with a patent plug, which allows the flask to be covered with nitrogen during the manufacturing process (due to the NeO / water reaction), and a thermometer for temperature control.
• a condenser water-cooled
• a stirrer with a patent plug, which allows the flask to be covered with nitrogen during the manufacturing process (due to the NeO / water reaction)
• a thermometer for temperature control.
• NCO target 6.24 ⁇ 0.1%
• the temperature is now kept at 75 ° C. for 3 hours.
• NCO target 0.00%
• item 4 is added and mixed thoroughly. After mixing, the reactor contents are cooled to approx. 40 ° C and the resin is filled.
• the parts refer to the weight.
• a paper web is made from a cellulose with a long fiber content of 80% in a paper machine.
• an aqueous emulsion according to Example 3 with a monomer content of 30 % is filled into the size press of the paper machine.
• the paper web is passed through the size press and impregnated.
• an electronic radiation curing system is set up, through which the paper web is passed.
• the result is an impregnated paper that has a resin content of 21% and is porous with high strength.
• the burst pressure is above 3 atmospheres.
• the resin is fully cured.

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• 1980
  • 1980-05-29 DE DE19803020333 patent/DE3020333C2/de not_active Expired
• 1981
  • 1981-05-23 EP EP19810103970 patent/EP0041205B1/fr not_active Expired
  • 1981-05-28 BR BR8103343A patent/BR8103343A/pt unknown
  • 1981-05-29 FI FI811664A patent/FI68436C/fi not_active IP Right Cessation

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