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
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/18—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising waxes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G9/00—Other accessories for paper-making machines
  • D21G9/009—Apparatus for glaze-coating paper webs

Definitions

• This invention relates to a method of preparing high-glaze waxed solid fibrous products, particularly paper or cardboard.
• paper products have been coated or impregnated with parafiin wax either by passing the web of paper over a roll partially immersed in molten wax, or by actually submerging the web of paper in the molten wax, the resulting waxed paper being then immediately subjected to a chilling (cooling) operation, either by passing it through cold water or by conducting it over cooling rolls, in order to impart a glaze to the surface of the coated paper.
• a chilling cooling
• the waxed paper prepared by the known processes often shows the undesirable crows-feet effect. This effect particularly occurs when the paper is passed at a relatively high speed through the molten wax and through the cooling water or over the cooling roll.
• the present invention comprises applying, for example, by coating or by impregnation, a moisture-proofing wax or waxy substance to a solid fibrous material, such as a web of paper, and rapidly cooling the treated fibrous material from a temperature of about or above the melting point of the waxy substance, i. e., a temperature at which the waxy substance is in the molten state, to a temperature substantially below the melting point of the waxy substance, by contacting it with mercury maintained at a temperature of not over about 30 C., preferably between about 0 C. and about 20 C.
• the waxy substance is preferably applied to the fibrous material in the molten state.
• the paper or cardboard can be actually submerged in the molten wax, or the paper can be passed over a roll partially immersed in molten wax, the roll picking up the wax and transferring it to the paper.
• the thickness of the wax film can be adjusted by means of scraper bars or by the pressure of a set of squeeze rolls. Other well known methods of applying the wax to the fibrous material can obviously be used in the present process.
• the parafiin wax can, for example, also be applied in the form of a solution in a volatile solvent to the fibrous material.
• the waxed product is then heated to a temperature of at least the melting point of the wax and subsequently chilled (cooled) according to the present invention. It is also possible to add the wax, preferably in the form of an emulsion, to the fibrous mass from which the paper or cardboard is prepared. The resulting waxed product is then heated to melt the wax and is then immediately cooled, using mercury as the cooling medium.
• the wax content of the resulting product may vary within wide limits.
• the wax content depends upon the density of the paper. the time allowed for penetration while the wax remains molten, the temperature of the wax, the type of wax, the pressure on the squeeze rolls, etc.
• the wax content is preferably at least by weight, calculated on the fibrous material to be treated.
• Any wax or waxy substance capable of moisture-proofing can be used.
• the most satisfactory materials are the paraflin waxes. Either macrocrystalline or microcrystalline wax, or mixtures of the two can be used.
• the microcrystalline paraffin waxes are generally more effective waterand moisture-proofing agents than the macrocrystalline type.
• the macrocrystalline waxes are, however, preferred for hot iinpregnation of paper because of their lower viscosities in the molten state. Generally, blends of the two waxes will be found to be the most satisfactory.
• paramn waxes are preferred, ceresins and some of the hard synthetic or manufactured waxes, as, for example, derivatives of the montan waxes or montanic waxes, can also be used, either instead of or in combination with the paraflin waxes, In general, the waxes which, relatively speaking, produce the best glaze in the conventional methods, will produce the highest glaze possible with the present invention.
• modifying agents can be incorporated in the waxy material used.
• the particular agents used for this purpose depend upon the properties desired in the final coating.
• certain resins both natural and synthetic, such as ester gum (i. e., esters of polyhydric alcohols, particularly glycerol, and resin acids), hydrogenated ester gum, rosin, polyethylene, oil-soluble alkyd resins, and the like, can be added to even further improve the brilliancy and gloss of the final coating.
• Other modifying agents which can be added include refined carnauba wax, Candelilla wax, the montan waxes or synthetic derivatives of montan wax, beeswax, Japan wax, ozokerite, and the like.
• the temperature of the mercury cooling bath should not be above about room temperature, that is, above about 30 C. Although a very high glaze can be obtained when the mercury bath is maintained at room temperature, most favorable results are obtained when the temperature of the mercury bath is between about 0 and 20 C. In general, the lower the temperature of the mercury bath, the higher is the glaze of the waxed product.
• any suitable cooling system can be used for maintaining the mercury at the proper temperature.
• the mercury bath can be cooled by indirect heat exchange with water, as by passing water through a cooling coil disposed in the mercury bath. This method of cooling is particularly suitable when maintaining the mercury at the relatively higher temperatures.
• Mercury does not adhere to paper or cardboard as does water, and, therefore, it can be used as a cooling medium for paper that has been waxed on only one side, whereas water cannot.
• the use of mercury has the further advantage that mercury does not adhere to the surface of the waxed product. Consequently, such costly equipment as scraping knives or vacuum installations, which equipment is generally associated with water cooling. is not necessary in the practice of the present invention.
• the surface of the waxed products prepared according to the method of the present invention is, generally, much more uniform than the surface of the waxed products glazed according to known methods of operation. For example, such irregularities as crows feet which frequently occur with the known processes, do not occur when using mercury as a cooling medium, even when the web of paper is passed through at a relatively high speed.
• the use of mercury as a cooling medium has the further unexpected advantage that the resulting waxed paper or cardboard has a greater imperviousness to water vapor than the waxed products obtained by cooling in air or by direct contact with water.
• EXAMPLE I Strips of paper weighing 40 grams per square meter, were passed through a vessel containing molten paraflin wax which was maintained at a temperature of 90 C.
• the paraffin wax applied was a macrocrystalline paraffin wax having a melting point of C.
• the paper was passed through the molten wax at a speed of 10 meters per minute so that it became impregnated with about 50% by weight, based on the paper, of paraflln Wax.
• the resulting waxed paper was immediately cooled. Four different tests were carried out using different cooling methods as follows:
• cooling was effected by passing the waxed paper through atmospheric air;
• the glaze of the waxed paper obtained in each test was determined by measuring the reflection in a gloss meter. The glaze measured is expressed as a percentage of reflected light.
• the same strips of paper were also measured for their permeability to water vapor.
• the permeability to water vapor is measured as the amount of water vapor (in grams) which, in 24 hours, passes from a vessel containing an atmosphere saturated with water vapor at 20 C. through 1 square meter of waxed paper into a vessel containing no water vapor.
• the results are set forth in Table II.
• waxed paper prepared according to the method of the present invention is considerably less permeable to water vapor than waxed paper which has been cooled in air or by contact with water at 4 C.
• I 1 In the method of preparing a waxed paper product wherein a web of paper is passed through molten paraflin wax and wherein the resulting wax-impregnated paper is immediately cooled to a temperature substantially below the melting point or the paraflin wax, the improvement comprising effecting said cooling by immersing said wax-impregnated paper in mercury maintained at a temperature of from about C. to about 20 C.
• paraflin wax is a mixture of macrocrystalline parafiin wax and microcrystalline paraflin wax.
• a method of preparing a waxed solid fibrous product which comprises contacting said solid fibrous material with a waxy substance in the molten state whereby said solid fibrous material is coated with the molten waxy substance, and passing the resulting wax-treated solid fibrous material through mercury maintained at a temperature of not more than 30 C. whereby said wax-treated solid fibrous material is cooled to a temperature substantially below the melting point of said waxy substance.

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  • NL NL74827D patent/NL74827C/xx active
• 1952
  • 1952-06-10 US US292746A patent/US2659683A/en not_active Expired - Lifetime
  • 1952-06-30 FR FR1059337D patent/FR1059337A/fr not_active Expired
  • 1952-07-01 DE DEN5732A patent/DE948842C/de not_active Expired
  • 1952-07-02 GB GB16659/52A patent/GB701360A/en not_active Expired

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