Method of securing stacked packages against slipping

United States Patent Office

3,598,677

Patented Aug. 10, 1971

3,598,677

METHOD OF SECURING STACKED PACKAGES AGAINST SLIPPING

Eduard Bergmeister, Hubert Wiest, Joseph Heckmaier, and Heinz Winkler, Burghausen, Upper Bavaria, Germany, assignors to Wacker-Chemie G.m.b.H., Munich, Bavaria, Germany

No Drawing. Original application Dec. 5, 1966, Ser. No. 598,897. Divided and this application Feb. 24, 1969, Ser. No. 801,814

Claims priority, application Germany, Dec. 24, 1965, W 40,595

Int. Cl. B32b 31/00

U.S. CL 156—276 7 Claims

ABSTRACT OF THE DISCLOSURE

Method of securing objects such as stacked packages of paper, cardboard and the like against slipping, in which adjacent contacting portions of such packages are united by an adhesive comprising an aqueous dispersion of a polymerizate of an olefinic unsaturated compound which forms a film at a temperature of not more than 4-10° C., in a homogeneous mixture with a substance selected from the group consisting of inorganic and organic pigments.

This application is a division of our pending application Ser. No. 598,897, filed Dec. 5, 1966, now abandoned.

It is quite a task to prevent stacked goods, which are packed in paper or cardboard, from slipping, i.e. shifting, during loading and shipping aboard vehicles running on or without rails, particularly railroads and trucks. This problem exists in an increasing degree in the case of goods packed on flat pallets, i.e. grid-like supports, on top of each other, in paper bags.

The slippage-preventing agents which have been used heretofore in an attempt to solve the above problem are aqueous alkali silicate solutions, starch solutions, rubber or natural resin dispersions. The alkali silicate solutions have the drawback that they have the effect of sticking so tenaciously that when the stacks are taken down the packings are damaged by tearing of the paper fibers, or after removal from the stacks films remain on the packing which crumbles easily and thus can easily contaminate the merchandise when the packages are emptied. Natural resin dispersions have the same drawback. The other anti-slipping adhesives that have been used heretofore could not be adjusted in their adhesive power to such an extent as to achieve a sufficient adhesive effect for reducing slippage in the stacks and at the same time to prevent damage to the packing due to tearing of the paper fibers or tearing of the packages when the stacks were removed.

Our invention provides a method of securing stacked packages against slipping while at the same time permitting such packages to be readily separated without tearing or otherwise damaging the packages, such as the fibers of paper bags when the latter are separated, and without crumbling or shredding in such a way as to contaminate the contents of the packages when the latter are opened and in use.

The adhesives which we use as anti-slipping agents are characterized by the fact that they comprise an aqueous dispersion of an olefinic unsaturated compound which forms a film at a temperature of not more than +10° C., in admixture with inorganic and/or organic pigments. The film forming temperature, also called “white point” or “lowest temperature for film forming” (for the definition see R. Houwink and A. J. Stavermann, “Chemistry and Technology of Plastics,” 4th ed., vol. II/2, p. 653) can be obtained from advertising pamphlets of the com2 mercially available polymerizate dispersions, or from the manufacturers of such dispersions, or it can be determined by applying the dispersion whose film-forming temperature is to be found in a thickness of 0.3 mm. (measured 5 on the moist, newly applied dispersion) on a glass plate by means of a film-forming apparatus and drying in a closed space (thermal chamber without air circulation).

Of aqueous dispersions from polymerizates of olefinic unsaturated compounds with a film-forming temperature 10 of not exceeding +10° C., those preferred are aqueous dispersions of polymerizates and/or copolymerizates of vinyl acetate with a film forming temperature of +10° C. at the most.

For the adhesives for use as anti-slippage agents ac15 cording to our method, very suitable are aqueous dispersions of polyvinyl acetate which contain plasticizers for polyvinyl acetate like dibutyl phthalate or tricresyl phosphate, and/or soft resins like low-molecular polyesters or polyvinyl ethers in quantities of 5 to 50 weight 20 percent, preferably 20 to 30 weight percent, always referred to the weight of the polyvinyl acetate, i.e. which are externally softened dispersions of polymerizates of vinyl acetate. At times these aqueous dispersions could also be dispersions of copolymerizates of vinyl acetate. 25 Examples of plasticizers for polyvinyl acetate, besides those named above, are esters of phosphoric acid like tributyl phosphate and diphenyl cresylphosphate, esters of phthalic acid like di-2-ethylhexyl phthalate and di-nbutylglycol phthalate, esters of adipic acid like dibutyl 30 adipate, dihexyl adipate and dioctyl adipate, esters of sebacic acid like diethylhexyl sebacate, dibutyl and dihexyl sebacate.

The manufacture of aqueous externally softened dispersions of polymerizates and/or copolymerizates of vinyl 35 acetate with a film forming temperature not exceeding +10° C. is well known.

Many externally softened polyvinyl acetate dispersions which are well suited for use according to our method are commercially available, for instance from Wacker40 Chemie G.m.b.H., Munich, Germany, under the names “Vinnapas-Dispersion M 54/25 C,” “Vinnapas-Dispersion M 54/25 TC” and “Vinnapas-Dispersion Z 54/20 C.” (The word “Vinnapas” is a registered trademark.)

Even more preferred than aqueous externally softened 45 dispersions of polymerizates or copolymerizates of vinyl acetate are those aqueous dispersions of copolymerizates of vinyl acetate with a film forming temperature not exceeding + 10° C. which can be called “aqueous, internally softened polyvinyl acetate dispersions.” The polymers in 50 the last-mentioned kind of dispersions are preferably copolymers of 30 to 90 weight percent vinyl acetate and 70 to 10 weight percent vinyl esters of saturated aliphatic monocarboxylic acids with 3 to 18 carbon atoms, like vinyl propionate, vinyl laurate or vinyl stearate, esters of 55 saturated aliphatic alcohols with 3 to 18 carbon atoms, aliphatic unsaturated dicarboxylic acids with 4 carbon atoms like maleic acid dibutyl ester, maleic acid di-2ethylhexyl ester, fumaric acid dibutyl ester or fumaric acid di-2-ethylhexyl ester, esters of saturated aliphatic 60 alcohols with 1 to 18 carbon atoms, of acrylic acid or methacrylic acid, like acrylic acid butyl ester and/or ethylene.

The manufacture of aqueous internally softened polyvinyl acetate dispersions with a film forming tempera65 ture of not exceeding +10° C. is well known. Some examples for copolymerizates of vinyl acetate which are principally contained in an aqueous internally softened polyvinyl acetate dispersion with a film forming temperature of not more than +10° C. are copolymerizates of 70 60% vinyl acetate and 40% maleic acid dibutyl ester 60% vinyl acetate and 40% vinyl laurate 75% vinyl acetate and 25% vinyl laurate

3,598,677 (Each of the above percentages refers to the total weight of the polymerizate.)

Many internally softened polyvinyl acetate dispersions which are even more suitable for application within the limits of the present invention than the externally soft- 5 ened polyvinyl acetate dispersions are available commercially, for instance from Wacker-Chemie G.m.b.H., Munich, Germany, under the names “Vinnapas-Dispersion 50/66 H,” “Vinnapas-Dispersion 50/40 VL,” “Vinnapas-Dispersion A 50/25 VL,” “Vinnapas-Dispersion Z 10 53/43 M” and “Vinnapas Dispersion Z 50/25 VL.”

One can use mixtures of various externally softened or of various internally softened or of externally softened and internally softened dispersions.

As inorganic or organic pigments one can use all fillers 15 which are not soluble in water or which are hard to dissolve in water, i.e. which dissolve not more than 1 weight part in 100 to 1000 weight parts of water at 20° C., which are inert towards the polymerizate dispersion, in the form of more or less dry powders. The following ex- 20 amples may be mentioned for such fillers: chalk, light spar, i.e. unburned ground gypsum, kaolin, silicon dioxide produced or precipitated pyrogenically in the gaseous phase, wood flour or products similar to wood flour like peanut shell flour and cork powder. Preferably one 25 uses 200 to 500, especially about 400 weight percent, always referred to the weight of the polymerizate, of fillers in the aqueous polymerizate dispersion which has a film forming temperature of not more than +10° C. One can also use mixtures of various fillers. 30

Against the above fillers in powder form, however, there are to be preferred as pigments aqueous dispersions of plastics, particularly of polymerizates of olefinic unsaturated compounds with a film forming temperature of at least +40° C.—because of the decreased danger of 35 the finished mixtures separating. One can also designate pigments of this kind as “finely dispersed particles used in the form of aqueous dispersions which do not form any film below +40° C., consisting of polymerizates of olefinic unsaturated compounds.” The upper limit of disper- 40 sions with film forming temperatures of at least +40° C. is not decisive. For instance, the film forming temperature of these dispersions may be 150° C. or more.

Among the preferred examples for polymerizates in aqueous dispersions of polymerizates of olefinic unsatu- 45 rated compounds with a film forming temperature of at least +40° C. may be named: Polyvinyl chloride, polystyrol, copolymerizates of 2 to 70 weight parts vinyl acetate and 98 to 30 weight percent vinyl chloride, copolymerizates of 70 to 95 weight percent styrol and 30 to 5 50 weight percent butadiene as well as copolymerizates of 70 to 95 weight percent acrylic nitrile and 30 to 5 weight percent butadiene.

The manufacture of aqueous dispersions of polymerizates of olefinic unsaturated compounds with a film form- 55 ing temperature of at least +40° C. is likewise well known. Some examples of copolymerizates which are contained in such dispersions, in particular are those of: 60% vinyl chloride and 40% vinyl acetate

85% styrol and 15% butadiene ⁶⁰

80% acrylic nitrile and 20% butadiene (Each of the above percentages refers to the total weight of the polymerizates.)

Many aqueous dispersions of polymerizates of olefinic 65 unsaturated compounds with a film forming temperature of at least +40° C. are available commercially, for instance from Wacker-Chemie G.m.b.H., Munich, Germany, under the name “Vinnol-Dispersion 45” and from the Chemical Works Hills A.G., Marl-Hills, Germany, 70 under the name “Litex SB 15.” (The name “Vinnol” as well as the name “Litex” are registered trademarks.)

One can use various aqueous dispersions with a film forming temperature of at least +40° C.

Preferably the aqueous dispersions with a film forming 75 temperature of at least +40° C. are used in such quantities that 20 to 500, especially from 60 to 200, weight percent (each time referred to the polymerizate in the aqueous polymerizate dispersion with a film forming temperature of not more than +10° C.) of the polymerizate of the aqueous polymerizate dispersion with a film forming temperature of at least +40° C. are available.

If one uses for pigments aqueous dispersions with a film forming temperature of at least +10° C., it is particularly helpful to use as aqueous dispersions with a film forming temperature of not more than +10° C. no dispersions containing any softeners, but to use internally softened polyvinyl acetate dispersions in order to avoid having the film forming temperature of the dispersion used as a pigment reduced by the softener content of the dispersions with a low film forming temperature.

It is preferred that the aqueous polymerizate dispersions with a film forming temperature of not more than + 10° C. as well as the aqueous polymerizate dispersions with film forming temperatures of at least +40° C. should have in each case 80 to 100 weight percent of the dispersed polymer particles with a diameter of a maximum of 2 microns. Such polymerizate dispersions are usually manufactured in accordance with known methods of the so-called “dispersion polymerization” or by emulsion polymerization.

The manufacture of the adhesives used as anti-slipping agents pursuant to our invention consists of mixing the compounds with each other until a homogeneous mixture is obtained. The temperature and pressure are of no consequence during mixing and during use of the antislipping agents. The water content of the anti-slipping agents can be adjusted to the viscosity required for each other.

The application of the anti-slipping agents is done by applying said anti-slipping agents during stacking to the sides of the packages that get in contact with the sides of other packages, and perhaps also to the side of the pallet which gets in contact with the first layer of packages, in each case immediately before the packages are placed upon it. The anti-slipping agents can be applied by spraying on or brushing on, e.g. with a brush or with a roller over the entire surface where slippage is to be prevented, or only on certain spots on these surfaces, e.g. by point or wave patterns. The anti-slipping agents are particularly useful for paper bags, but they can also be used effectively on cartons made of full or corrugated cardboard and folding boxes and other packaging materials made of paper or cardboard.

The anti-slipping agents disclosed herein will bind within one-half to one whole hour aifter application, and even if application is made only in certain spots the result is safe stacks which will not slip during loading or transportation. The packages can be separated again easily and without damage. The film remaining on the packages adheres firmly to the package surfaces, it is pliable and will not crumble even when the surfaces are bent.

The parts and percentages shown in the examples below refer in each case to the weight. The percentages are calculated in each case for the total weight of the dispersions, provided nothing to the contrary is stated.

EXAMPLE 1 parts of a 50% aqueous dispersion of a copolymerizate of 60 parts vinyl acetate and 40 parts vinyl laurate, with a film forming temperature of 0° C., containing as a dispersion agent about 3 percent polyvinyl alcohol with the saponification number (milligrams KOH, required for splitting off and neutralizing the remaining acetyl groups in 1 g. polyvinyl alcohol) of 140 and wherein at least 80% of the dispersed polymer particles have diameters within the range from 1 to 2 microns, are stirred with 133 parts light spar which were first mixed with 75 parts water, until a homogeneous mix is obtained.

3,598,677 ⁵ .

The anti-slipping agent obtained in this manner is properly diluted before use with three parts of water per one part of anti-slipping agent.

EXAMPLE 2 parts of an aqueous dispersion with a film forming temperature of below 0° C. containing 43% polyvinyl acetate, as a softener 11% dibutyl phthalate and as a dispersion agent about 3% polyvinyl alcohol with a saponification number of 140, and wherein at least 80% of the dispersed polymer particles have diameters in the range from 1 to 2 microns, are stirred with 140 parts chalk which were first mixed with 100 parts water until a homogeneous mix is obtained.

The anti-slipping agent obtained in this manner can be diluted before use with up to 4 parts water per part of anti-slipping-agent.

EXAMPLE 3

100 parts of an aqueous dispersion of a copolymerizate with a film forming temperature of 0° C., of 75 parts vinyl acetate and 25 parts vinyl laurate, containing as a dispersion agent about 3% of a phenolpoly oxethylene glycol ether available commercially as an emulsifier and 0.3% sec. sodium Ci₄_₁₅-alkyl-sulfonate, and wherein at least 80% of the dispersed polymer particles have a diameter of about 0.1 micron, are stirred with 80 parts of an aqueous dispersion with a film forming temperature of over 100° C., containing 45% polyvinyl chloride and as a dispersion agent 2% sodium lauryl sulfate, and wherein at least 80% of the polymer particles have a diameter of less than 0.5 micron; and with 550 parts of water, to form a homogeneous mixture.

EXAMPLE 4

100 parts of the dispersion described in Example 3 as a dispersion with a film forming temperature of 0° C. are stirred with 80 parts of a 45% aqueous dispersion of a mixed polymerizate with a film forming temperature of 60° C. containing 60 parts vinyl chloride and 40 parts vinyl acetate, and containing as a dispersion agent 2% sodium lauryl sulfate, and wherein at least 80% of the polymer particles have a diameter of less than 0.5 micron; and with 500 parts of water, until a homogeneous mixture is formed.

EXAMPLE 5

100 parts of an aqueous dispersion with a film forming temperature of 4-6° C. containing 50% of a copolymerizate of 60 parts vinyl acetate and 40 parts maleic acid dibutyl ester and as a dispersion agent 0.5% polyvinyl alcohol with a saponification number of 140, 0.33% of a mixture of 1 part sodium cetyl sulfate and 1 part sodium stearyl sulfate and 0.75% of a cetyl polyoxy ethylene glycol ether with an average of about 10 oxyethylene units per molecule, and wherein at least 80% of the dispersed polymer particles have a diameter in the range from 0.5 to 2 microns, are stirred with 100 parts of an aqueous dispersion with a film forming temperature of over 100° C. which contains 50% of a copolymerizate of 85 parts styrol and 15 parts butadiene and as a dispersion agent 4% sec. sodium C₁₄_₁₅=alkyl sulfonate, and wherein at least 80% of the dispersed polymer particles have a diameter of below 0.5 micron; and with 800 parts of water, until a homogeneous mixture is formed.

EXAMPLE 6

100 parts of the dispersion described in Example 3 as a dispersion with a film forming temperature of 0° C. are stirred with 100 parts of an aqueous dispersion with a film forming temperature of over 100° C. containing 50% of a copolymerizate of 80 parts acrylonitrile and 20 parts butadiene and as a dispersion agent 4% sec. sodium ⁶

Ci₄_i5=alkyl sulfonate, and wherein at least 80% of the dispersed polymer particles have a diameter of less than

0.5 micron: and 1000 parts of water, until a homogeneous mixture is formed.

The mixtures produced in accordance with Examples 1 through 6 are used in such a manner that 4 squirts (each about 3 ml.) of each mixture are applied from a polyethylene spray bottle by hand pressure to a paper bag and the next bag is laid on the treated side of the first bag. After 40 hours the bags are separated. No damage to the paper occurs, and the films of the adhesive will not crumble off even if the paper is creased.

All temperatures shown above and in the appended claims, in front of which there is no plus sign (4-) represent temperatures above 0° C. if there is no minus sign (—) in front of them and if the temperature shown is not “0° C.”