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
  • D21H17/63—Inorganic compounds
  • D21H17/66—Salts, e.g. alums
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/907—Resistant against plant or animal attack

Definitions

• c1 117/113, corrugated board are made resistant gnawing y rodents y 117/60, 117/76 P, l 17/ 152, 117/169 impregnating the product with ammonium alum or potassium 511 1111.
• c1 B4411 1/06, alum- Ranges of amounts of impregnam and of conditions for D2111 1/10, D211 5 /22 impregnation procedure are set forth.
• This invention relates to the impregnation of fibrous material including felted cellulosic materials such as paperboard and corrugated container board for the purpose of discouraging or preventing rodents from gnawing through the material.
• the invention is particularly useful in the manufacture of shipping or storage containers for food and for the erection of static storage facilities such as bins and the like for food intended for human consumption.
• the present invention provides the impregnation of the material with potassium alum or ammonium alum within relative narrow ranges of conditions to accomplish the required degree of uniformity of penetration.
• a good method of testing rodent resistance of a packaging or constructional material for the shipping and storage of food consists of the following steps.
• the rodent is placed in one end of a cage and food is placed in the other.
• the ends are separated by a vertical barrier made of the material to be tested.
• the barrier is raised above the floor of the cage a sufficient amount so that the rodent is aware of the food.
• Furthermore the raising of the barrier gives the rodent an edge on which to secure his teeth in an attempt to gnaw through the barrier to reach the food.
• the rodent is not fed for a considerable period of time prior to being put into the test cage. During the test, while the rodent is in the cage, it is given unlimited water, i.e. ad libitum.
• the time required for the rodent to go through the barrier is a measure of the rodentproofness of the material. In the extreme the rodent never gnaws through the barrier and dies. In tests of the material of the present invention in the vast majority of cases the rodent completely failed to gnaw the material and in other instances the rodent caused only superficial damage and did not persist in gnawing to such extent as to accomplish passage through the barrier.
• fibrous products are impregnated by immersing the same in a bath made up of molten ammonium or potassium alum diluted with water and maintained at an elevated temperature.
• the relative amounts of molten alum and water and the temperature of the bath are maintained within rather narrow ranges to achieve the type of impregnation best calculated to achieve the increase in strength and the other characteristics provided in 5 id patents.
• the ranges set forth in aid patents impart a great deal of stiffness to the impregnated product but when considered from the standpoint of very small increments of area or thickness of the product do not necessarily result in uniformity of distribution of the impregnant within the fibrous structure of the product.
• the alum may be quite highly concentrated in the regions near the opposite major surfaces of the product and quite low in concentration or absent altogether in the central regions of the thickness of the product.
• the relatively high specific gravities and relatively high temperatures constituting the preferred ranges set forth in said patents result in somewhat uneven distribution patterns in the zones of highest concentration of the impregnant. Such unevenness exists between surface increments or thickness increments which are sufficiently small when compared with the size and thickness of the product as to be of no consequence from the standpoint of strength or stiffness of the final product.
• the distribution of the alum penetrant in the fibrous structure of the product must be quite even in all three dimensions of each element of the product.
• the distribution should be substantially uniform in concentration in the lengthwise and widthwise dimensions and also should be at least devoid of sharply changing layers of concentration through the thickness of the fibrous product.
• concentration of penetrant throughout the thickness of the product could be made uniform or substantially so but from a practical standpoint absolute uniformity would be difficult if not impossible to achieve.
• the present invention provides ranges of operating procedures and other techniques to achieve the type of penetrant distribution required for maximum rodent resistance.
• the present invention is applicable to'any fibrous product which is customarily used in the container and paperboard fields such as fiber board, corrugated board or corrugating medium made of any of the usual fibrous materials such as virgin pulps from wood, sisal, straw etc., or secondary pulps such as used in chipboard, newsboard and the like or mixtures of any of these pulps. Also it is applicable to containers, container elements, tubes and the like made from such materials.
• a particular product with which the present invention is very advantageous is corrugated board made up of one or more liner boards laminated with one or more plies of corrugating medium.
• Liner boards used in the manufacture of corrugated board sometimes have one surface which is smoother than the other. Particularly when the smoother surface has been calendered it is a customary practice to arrange the less smooth surface inside the structure to take advantage of the better pasting" characteristics of such surface, which is more easily penetrated by the adhesive. For the purposes of the present invention is is preferable to arrange the less smooth surface, when there is a difference, to lie outside the corrugated structure thus to take advantage of the greater penetrability of such surface to promote uniformity and depth of penetration of the outer surfaces by the alum-water bath. If so desired the paperboard may be deliberately manufactured in such a way as to have both surfaces readily penetrable by the alum-water bath. For example, calendering of either surface may be omitted.
• the rapidity, evenness and depth of penetration may be enhanced when so desired by steaming the fibrous product just prior to immersion into the alum-water bath. It also has been observed that there is a tendency for the upper surface regions of the alum-water bath to have a higher concentration of alum than the remaining regions. Thus when a fibrous product is withdrawn from the bath there is some tendency toward the deposit, on the surface of the product, of a superficial layer of more concentrated alum which sometimes crystallizes and degrades the appearance of the final product.
• the steaming of the product before immersion can be carried out by arranging nozzles supplied with low-pressure steam, say 50 p.s.i.g. or less, directed upon the product as it enters the bath.
• Steam nozzles also may be directed onto the upper surface of the bath to minimize the superficial deposit just mentioned. 1f the steam nozzles are also directed on the product as it emerges from the bath the steam will be effective to even out the surface distribution of the alum, thus promoting the rodent resistance thereof while also improving the surface appearance by minimizing surface bloom.
• sodium alum, Na SO.,- (SO -24H O is not suitable as an impregnant for the present invention, with either ammonium alum, Al S (NH.,) SO 24H O, or potassium alum, Al (SO.,) -l( 50,2411 O
• penetration is enhanced by adding to the alum-water bath a sodium ion source.
• the mass percent of sodium added should be from about 3 percent to about 6 percent of the total mass of the alum in the bath. Lesser quantities of such additive have little effect while greater quantities cause the final product to be undesirably weak or limp.
• the sodium may be add ed in the form of sodium silicate or sodium sulfate, for example.
• wetting agent which does not salt out readily at the temperature and pH of the particular bath may be used, for example, sodium dihexyl sulfo succinate may be added in the proportion of about 0.25 to 1.0 percent (based on total weight of the bath).
• the addition of sodium and/or a wetting agent to the alumwater bath may be made with the specific gravity and the temperature of the bath maintain at any point within the best or acceptable ranges which will be discussed below. Since dif ferent fibrous products may have somewhat different characteristics with regard to imbibing or accepting penetration by the molten alum the use of one or both of such penetrationpromoting additives will be most useful when the particular fibrous product at hand is relatively difiicult to penetrate. Also such addition may make it possible to operate at somewhat higher specific gravities in the treatment of fibrous products of different characteristics. In a very general sense the achievement of deep and evenly distributed penetration appears to be accomplished when the specific gravity and temperature of the bath are both maintained toward the lower regions of the ranges set forth below and the use of additives frequently is very helpful in operations in the upper regions of said ranges.
• ammonium alum-water bath temperature is best maintained from about 94 C to about 99 C. when the specific gravity of the bath lies within the ranges given below.
• the comparable temperatures for the use of potassium alum are from about 93 C. to about 97 C. These temperature ranges give best results. Acceptable results for ammonium alum can be achieved in the range of 99 C. to 104 C.
• the analogous temperatures are 97 C. to 102 C.
• Ammonium alum melts at 93.5 C. and in its undiluted molten state has a specific gravity of about 1.550.
• Potassium alum melts at 92.0 C. and in its undiluted molten state has a specific gravity of about 1.70
• the specific gravity of the bath is made quite low by water addition.
• ammonium alum is is made from about 1.325 to 1.375 for best result but acceptable results can be had within the range of about 1.325 to about 1.452.
• potassium alum best results are secured in the specific gravity range of from about 1.315 to about 1.380 and acceptable results can be achieved from about 1 .315 to about L440.
• the best range for impregnation as regards temperature and specific gravity a typical fibrous product namely, corrugated board may be caused go pick up alum in well-distributed form in an amount preferably in the range of from about percent to about 220 percent of the weight of the unimpregnated product. This is regarded as the best range and will be referred to hereinbelow. Smaller pickup percentages down to about 50 percent of the weight of the unimpregnated product are useful but as will be pointed out below are somewhat less rodent resistant.
• rodent attack occurs on 5 percent or less of the total area with no boring through.
• rodent attack occurs on 50 percent or less of the surface area and some boring through occurs but usually not to such an extent as to permit passage of the rodent through any openings thus made.
• the pickup ratio is permitted to drop down to about 50 percent but with the specific gravity and temperature lying within the best ranges
• rodent attack occurs on 50 percent of the surface area, marginal boring through occurs on about half of the sample barriers and full boring through occurs only on about 10 percent of such barriers. Results of the latter type also occur when the specific gravity or temperature of the bath lies within the upper limits of the acceptable ranges. It will be apparent that reduction of full boring through to about 10 percent is nevertheless a substantial accomplishment when it is considered that standard corrugated board can not be regarded as having any practical rodent resistance.
• the surface appearance is correlated to the conditions of pickup percentage, temperature and specific gravity in about the same manner as is the rodent resistance. That is when the product is unevenly or superficially impregnated more than 5 percent of the surface of the final product be covered by crystalline impregnant. This also is particularly noted in operations at the higher temperatures and specific gravities especially in the absence of wetting agents or sodium. It is also noted when the percentage pickup is permitted to rise substantially above about 220 percent. Thus from a visual standpoint operations outside the preferred ranges usually will produce mottling or blooming observable by the unaided human eye and affecting more than 5 percent of the surface area.
• a waterproof coating to the alum-impregnated product this may be done by passing the material either cold or hot through a flowing curtain of molten waterproof material.
• a typical waterproof material is vinyl acetate-ethylene copolymer percent; petroleum hydrocarbon resins 10 percent; paraffin 75 percent. Any material that gives continuous film characteristics to the coating, such as paraffin-montan wax mixture is effective.
• the surface of the coated products will show to the unaided human eye a mottled appearance in which more than 5 percent of the surface will have a different color or shade, if the alum impregnation is not carried out within the preferred or acceptable ranges set forth above.
• Such waterproof coatings may be desirable for containers or storage structures which are to be exposed to the weather or to other adverse moisture conditions. Although most waterproof coatings are themselves flammable the addition of such coatings to the alumtreated products of the present invention does not substantially degrade the fire-resistant characteristics of the alumtreated products. This is in considerable contrast with those fibrous products which are impregnated with flammable materials instead of being thinly coated as is the case in the waterproofing of the product of this invention. The waterproof coating appears to have little, if any, effect upon the rodent resistance of the alum-impregnated material.
• a fibrous material such as paperboard impregnated with an impregnant consisting essentially of an alum selected from the group consisting of ammonium alum and potassium alum and a sodium ion source in quantity sufficient to provide in said impregnant from about 3 percent to about 6 percent by weight of sodium ions based on the weight of said selected alum in said impregnant and in which the weight of said alum contained in said impregnant is within the range of from about 50 percent to about 220 percent of the weight of the fibrous material before impregnation, said impregnated fibrous material being rodent resistant due to the fact that the distribution of the alum contained in said impregnant within said fibrous material is sufficiently widespread and uniform that less than 5 percent of the original surface of said fibrous material is hidden by alum in visible form.
• a fibrous material according to claim 1 or claim 2 which has a superficial coating of water-resisting material which is so uniform in appearance that less than 5 percent of the surface of the coated material is detectable by human unaided eye to be of a different shade or color than the remainder of the area of said surface.
• a process for producing a strengthened impregnated rodent-resistant fibrous material such as paperboard which comprises:
• impregnating said fibrous material by treating the same in an impregnating bath consisting essentially of an alum in molten form selected from the group consisting of ammonium alum and potassium alum and a sodium ion source in quantity sufficient to provide in said impregnating bath from about 3 percent to about 6 percent by weight of sodium ions based upon the weight of said selected alum in said impregnating bath,
• a process for producing a strengthened impregnant rodent-resistant fibrous material such as paperboard which comprises:
• impregnating said fibrous material by treating the same in an impregnating bath consisting essentially of an alum in molten form selected from the group consisting of ammonium alum and potassium alum,
• said impregnating bath is a continuous body of liquid and in which said treating step and said terminating step are performed respectively by dipping said fibrous material into and removing said fibrous material from said body of liquid through a surface of said body, and in which said surface of said body is continuously showered with stem to cause local dilution of those portions of said body of liquid which are adjacent said surface.
• line 52 "2220 should be --22o-- Col. 4, line 73 before "he” insert -will- Col. 5, line 62 "20” should be --22o-- Claim 2 o 001. 6, line on "stem” should'be -'-steam-- (Claim 9) Signed and sealed this 20th day of June 1972.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Paper (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9849918

Family Applications (1)

Country Status (9)

Citations (8)

• 1968
  • 1968-02-20 GB GB8302/68A patent/GB1184035A/en not_active Expired
  • 1968-12-05 US US781631A patent/US3632408A/en not_active Expired - Lifetime
• 1969
  • 1969-02-05 IL IL31561A patent/IL31561A/en unknown
  • 1969-02-14 NL NL696902430A patent/NL147808B/xx not_active IP Right Cessation
  • 1969-02-18 FR FR6904031A patent/FR2002233A1/fr not_active Withdrawn
  • 1969-02-18 BE BE728577D patent/BE728577A/xx not_active IP Right Cessation
  • 1969-02-19 JP JP1246869A patent/JPS541802B1/ja active Pending
  • 1969-02-19 CH CH253669A patent/CH498245A/fr not_active IP Right Cessation
  • 1969-02-19 IT IT35093/69A patent/IT941523B/it active

Patent Citations (8)

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