DE2062299A1 - Polymer-impregnated cardboard - Google Patents

Description

Polymer impregnated cardboard (priority: December 1, 1969 - Canada - No. 070 454)

The present invention relates to a paperboard sheet and a method for making the same, wherein the paperboard from which the sheet is made is treated with a hydrocarbon polymer to an absorption of 5 to 80% based on the untreated weight of the paperboard, and wherein the hydrocarbon polymer is cured in situ on the cardboard.

The present invention thus relates to impregnated cardboard and in particular corrugated cardboard with moisture and dry resistance, which has been impregnated with a specific polymer and the process for the production of such cardboard.

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The corrugated board industry has always sought an improved paperboard that was both dry and dry Has moisture stiffness and still retains the ability to split. Many different waterproofing agents have been tried to increase this strength. However, this problem is not easy as it is not just a matter of strength, but also the preservation of the foldability and of course the costs are extremely important.

To the knowledge of the applicant, the only impregnated articles used in the art are those made from phenolic urea or melamine-type impregnated paperboard coated with the mass of rigid, moist containers made of wax or Wax impregnated cardboard.

Some of the cardboards available have a relatively high compressive strength when wet, for example with melamine urea or phenolic resins. However, these products generally have a relatively low level Dry and puncture tear resistance and are not foldable once under technically acceptable handling conditions have been processed.

One of the better products requires impregnation with wax up to a relatively high degree of absorption, to get a paperboard that has acceptable wet and dry strength. Because of the high intake required however, such cardboard is relatively expensive.

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The present invention is based on the finding that by impregnating the outer parts and the middle pieces of a cardboard sheet in a special way with a selected one Impregnation agent up to a specific degree of impregnation a more economical cardboard can be obtained, which have both good moisture and dry strength and has satisfactory foldability. A specific polymer selected in the present invention will generally be regarded as an unsuitable product for the petro-industry and contains cyclic and acyclic diolefins with 5 to 6 carbon atoms and a high degree of unsaturation.

The present invention relates generally to a paperboard sheet impregnated with a hydrocarbon polymer containing cyclic and acyclic diolefins having 5 to 6 carbon atoms and a high degree of unsaturation to ensure a resin pick-up in the range of 5 to 40 % , and wherein the resin is cured in situ in the cardboard.

The other features and advantages are from the following detailed description can be seen in connection with the accompanying drawings, wherein

, Fig. 1 is a schematic diagram illustrating a Illustrated procedure for the production of a combined paperboard; .

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Fig. 2 is a schematic diagram showing another of the present invention Manufacturing method of a container explained;

Fig. 3

and FIG. 4 are diagrams similar to the present invention Products with regard to moisture and dry compressive strength to compare; and

Fig. 5 shows a graph showing the change in tensile strength in the direction of the machine in relation to vid in the opposite direction for the absorption of impregnation agents.

One of the preferred polymers is that sold by Imperial Oil Limited under the trademark CTLA. One typical analysis of this polymer is given in Table 1.

Table I.

spec. Weight, API 9.2

Viscosity SSU at 99 ° C 205

Flash point, COC ⁰ C 154

Iodine number cg./g. 255

Ash wt % 0.06

Non-volatile constituents wt.% 95 Color, Gardner (1 g.CTLA in 67 mil.Wasser, weiss.Xylol) 10

Acid number, mg. KOH / g. ⁰ C 0.1 Saponification number, mg.KOH / g. 3.18 Surface tension, dynes / cm. 44.5 Distillation at 10 mm. (ASTM D 1160), IBP 83 5 % 148 10 % 163 20 % 192 30 % 218 40 % 240 50 %. (split) 262

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The polymers contain cyclic and acyclic diolefins having 5 to 6 carbon atoms, along with or without minor Amounts of styrene, indene and other unsaturated aromatics Connections and are made from the original loan Petroleum extract through polymerization over an alumina catalyst. It is only partially polymerized and has a low molecular weight. The polymer is viscous, dark brown and soluble in benzene, acetone, kerosene, methylene chloride, varsol, etc.

As indicated above, the preferred polymer is generally considered to be an unusable product; the chemical Composition cannot be given with perfect accuracy.

In the specification and claims, the term "hydrocarbon ^{polymer 11} " means the CTLA polymer as indicated above or its equivalents.

If the cardboard according to the invention is to be formed from a group of containers per se, the container cardboard can either coated or impregnated with hydrocarbon polymer. The amount of polymer that can be incorporated is in the range from 5 to 40%, based on the untreated Weight of the sheet. It should be noted that if a foldable carton is to be made, i.e. one that does not tear, or at the fold lines, then the total resin concentration

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tration in the material should preferably be less than about 26 % of the untreated weight of the sheet and in any case not exceed 50% , otherwise the paperboard will have an unacceptable foldability. In general, such low uptakes are obtained by coating, in particular for uptake below 20 % with uptake between 20 and 26 % , an impregnation technique should preferably be used. The paperboard will generally not be impregnated to above about 40% pick-up for reasons discussed below.

One must be careful when making the impregnated cardboard, otherwise an unacceptable cardboard will be obtained will. It has been found that the combined paperboard and container sheets according to the invention according to one of the two Paths should be made. One process is illustrated schematically in Figure 1, wherein each of the components is separated coated, impregnated and then combined and the other process shown schematically in Fig. "2, wherein the combined container sheet is evenly impregnated by immersion in the hydrocarbon copolymer.

With reference to FIG. 1, the central part 10 is coated on one side at the coating station 12, so that the side of the central part facing away from the coater is approximately 80 % untreated. This allows a resin uptake of about 20 %, based on the untreated law of the middle

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part. This treated central portion is corrugated at corrugation station 16 and an adhesive is applied to the heads of the ribs which are formed on the presented, essentially polymer-free surface. At the same time, a first lining 18 is coated on the outer surface up to a resin receptacle, the inner surface being at least 80 % polymer-free. The inner surface of the first liner is then moved into contact with the adhesive on the ribs of the central part and the central part and the first liner are anchored together into the single sheet 20.

The only path 20 leads on to the double pressing and hot plate 22, where a second liner 24 _s is treated in the coater 26 on its outer surface so that the inner surface is substantially LiNb © is, that is, the inner surface is substantially 80 % resin-freeϊ this inner surface is applied to the free heights of the ribs of the only sheet to which adhesive has been previously applied. The combined paperboard is then formed by curing the adhesive in the hot plate zone. The hydrocarbon polymer is also at least partially cured as the combined paperboard passes through the hot plate area.

To achieve the desired degree of impregnation is it has been found that the hydrocarbon polymer is maintained at least at a temperature between 26.7 and 49 ° C must be »if the correct polymer uptake can be achieved

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target. In certain cases a solvent can also be used.

With this process, each element of the combined paperboard, ie the liner and centerpiece, receive a gradient in polymer concentration extending through their thickness and are typically treated with resin pickups in the range of 5-20 % based on the untreated weight of each component been.

"One of the advantages of this procedure, being every single one Component is treated separately, it is that there is an impregnation of each component to its optimal degree of penetration allowed, within the possible limits, without causing hardening difficulties with common adhesives. For some uses it may even be appropriate to use only the inner liner or the inner liner and the center piece or outer liner, or a combination, depending on the particular application being made

I impregnate cardboard.

The combined paperboard, according to the procedure described above, is generally used when reinforced Cardboard is required and high humidity is expected, but it is not recommended for immersion in water. Some difficulties can arise when gluing such cardboard with conventional adhesives, so that the Folded edges or gluing with adhesive tape is recommended.

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The procedure described so far closes this Coating of the lining and the middle part directly on the corrugating machine. These linings and the central part can, on the other hand, be precoated before being fed to the corrugating device and just go through this wave device. Also, in the system described above, each of the Linings and the middle part are coated with the polymer. If for some applications only one or more of these elements that make up the combined paperboard need to be coated, so of course only this should selected element to be coated.

Another way of making cardboard boxes accordingly of the present invention is shown in Figure 2, wherein here a cardboard sheet 30 is made with in the usual way or without completing the manufacturer's connection (manufacturer's joint) and then impregnated with a polymer solution of the desired concentration and temperature (according to the desired Degree of addition) by dipping into an impregnation tank 32 and held there for the desired time, for uniformity Distribution.of the polymer in the fiber matrix is allowed to drain and then the impregnated sheet is passed into an oven 34 or the like where the polymer is in situ in the sheet is hardened.

According to the latter procedure, the sheet 30 is immersed in a tank 32 which holds the polymer at a

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Temperature in the range between about 26.7 and 82 ° C for 3 to 10 minutes, generally about 5 minutes to obtain the desired resin pick-up, which ranges from about 20 to 40 % based on the untreated weight of the sheet amounts to. Preferably, the resin absorption is in the range of 22 to 35 wt.% Of the untreated sheet and, in general, except for special cases, they can not exceed 40%. If the total amount of resin in the sheet is higher than specified; so the leaf becomes unnecessarily discolored and actually begins to lose its tensile strength noticeably. The curing of the resin in oven 34 takes about 10 to 25 minutes, at a temperature in the range of 177 to 232 ° C, preferably about 190 to 213 ° C.

As indicated above, a combined paperboard impregnated with the selected hydrocarbon polymer provides a product with unexpected physical properties which is particularly useful in the packaging industry, for example for containers. A comparison of the present invention made of cardboard, and other common products ¹ is given in Table II and FIGS. 3 to 5 inclusive.

The term "wax coated" as used in Table I and in the drawings refers to a corrugated board having about 15 % wax in the central portion and about 10 % on each of the liners. The term "wax impregnated" refers to

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on a cardboard which has been dipped in wax and treated to a wax pick-up of approximately 50%, based on the untreated weight. Phenolic-impregnated paperboard refers to paperboard that contains 3 to 4% phenolic resin, and melamine- impregnated paperboard contains 15% melamine resin

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Table II

wax impregnated

wax-coated

polymer

polymer

Basis weight of the
combined cardboard

231

211

209

150

Lining middle part
Liner basis weight

42/26/42

69/26/69

69/26/69

42/26/42

- * recording ι Zerissfestigk.g. Dip-impregnated, 10% wax in DecK - Impregnated Impregnated ISJ I. O Ribs about 50 % layers, with 1 polymer with CB67-1 _ ... -. ο co 50 % relative humidity Addition of wax 15% wax in the mit solution, 23.2 % Solution, 25 % -SJ if OO 90 % relative humidity central part Addition schlei Addition schlei SJ 24 hours in water veil-coated coated coated 225 ^ immersed on both sides on both sides. on both sides. 295 cd Il Column compression - CD 50 % relative humidity 245 241 380 257 «w 200 * - * 90 % relative humidity 158 96 300 190 ** 24 hours of water 54 40 96 66 ι submerged Ready to tear 50 % relative humidity 275 395 366 279 90 % relative humidity 330 351 375 279 24 hours of water
submerged 205
i 264 200 99 _ . ■ " 420 425 381 600 560 585 325 365. 466

With reference to Table II it is clear that for paperboard with equivalent basis weight the column compressive strength "at 50 % relative humidity, 90 % relative humidity or after 24 hours of immersion in water is higher for the products manufactured according to the invention than for either of the other two comparison products. It can be further established It can be seen that the cardboard according to the invention with the lower basis weight is stronger in the compressive strength strength at high humidity and after immersion than the other two products tested.

The puncture tear strength and the tear strength on the ribs on boards of similar basis weight are essentially comparable or satisfactory.

It can also be clearly seen from FIG. 3 that the wet compressive strength of the cardboard impregnated with the polymer, in particular a cardboard with approximately 30 % absorption, is very high and almost reaches that of a melamine-impregnated cardboard. Similarly, the dry strength of the polymer impregnated paperboard in the preferred impregnation range is about 30 % higher than any of the available products, being about 80 points higher than the melamine impregnated paperboard,

When comparing the physical properties of the inventive Cardboard with the known one must be noted that the cardboard according to the invention is generally cheaper than any of the other paperboards with equivalent properties.

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As indicated above, the foldability of the paperboard is not impaired with the hydrocarbon polymer content in the specified amount, as is normally the case when the paperboard has been impregnated with resin. It has been found that cardboard treated as described above with a 25 to 40 % pick-up can be subjected to an essentially unlimited number of 360 ° folds when the folds are either parallel or transverse to the ribs. This is not generally so for the thermosetting impregnation resins.

In a study by J.W. Konning and D.J. Fahej, U.S. Forest Products Lab, Madison Wisconsin, published in "Phenol Reson Treatment Improves Fiberboard Compression Strength" (Pachage Engineering, October 1965) has been found to be generally with respect to the thermosetting resins the foldability of the cardboard obtained decreases.

specified, it must be ensured that the recommended additional ranges are not exceeded, otherwise the tensile strength of the material is greatly reduced. This can be clearly seen from Fig. 5, which is an impregnated lined Comparing cardboard at different levels of impregnation and indicates its ultimate tensile strength. So it can be determined that after an impregnation range of about 30 the tensile strength decreases at a very high rate.

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Claims (17)

Claims M .J combined cardboard for making cardboard boxes with, high Feüchtfestigkeit and dry compression strength of einenL-P ^ ar AuskleMun ^ enLJbzw _A cover layers and a corrugated middle piece between the liners, characterized in that the cardboard between 5 and 40 wt.%, Based to the untreated weight of the paperboard of a polymer containing primarily cyclic and acyclic diolefins having 5 to 6 carbon atoms, the polymer having been cured in situ in the liners and centerpiece. " 2. Combined paperboard according to claim 1, characterized in that it contains a hydrocarbon polymer. 3. Combined paperboard according to claim 2, characterized in that at least one of the linings or the middle section contains 5 to 20% of the hydrocarbon polymer, not evenly distributed in its thickness, such that a surface of the liner and centerpiece is substantially free of the hydrocarbon polymer is. . 4. Combined paperboard according to claim 2, characterized in that it contains from 20 to 40 % of the hydrocarbon polymer, based on the untreated weight of the paperboard, and this is uniformly distributed in the thickness of the liner and the center piece. 109826/1107 5. A method for producing a container sheet from a combined cardboard with a liner and a corrugated inner part in between, characterized in that the liner and the corrugated inner part with a hydrocarbon polymer up to an absorption of 5 to 40 %, based on the untreated weight of the Cardboard treats and . the hydrocarbon polymer cures in situ in the liners and midsection. 6. The method according to claim 5, characterized in that at least one of the lining pairs and the center piece are treated individually up to an absorption of $ 5 to 20% by weight , based on the dry weight of the lining and the center part, then combined to form the cut out a combination of cardboard and a tray sheet. 7. The method according to claim 6, characterized in that each outer part and the inner part is treated only from one side to a non-uniform distribution of the hydrocarbon polymer in the thickness of the outer parts and the central part, a surface of the outer parts and the central part at least 80 % free is from the hydrocarbon polymer. 8. The method according to claim 7, characterized in that the outer parts and the central part with the hydrocarbon polymer at a temperature of 27 Treated up to 82 ° C. 109826/1167 Process according to Claim 5, characterized in that the outer parts and the central part are treated after the production of the container sheet by impregnating the container sheet with the hydrocarbon polymer to an absorption of 20 to 40%, based on the untreated weight of the sheet. 10. The method according to claim 9 »characterized in that the piece after impregnation in heated in an oven for 3 to 10 minutes at 177 to 232 ° C is to put the hydrocarbon polymer in situ in the piece to harden. 11. The method according to claim 10, characterized in that the piece with the hydrocarbon polymer impregnated at 49 to 82 ° C. 12. The method according to claim 11, characterized in that the sheet is impregnated with the hydrocarbon polymer up to an absorption of 22 to 35% _t based on the untreated weight of the piece. 13. cardboard for making cardboard boxes according to claim 1, characterized in that it comprises a cardboard box based on cellulose with between 5 and 40 wt.%, Based on the untreated weight of the cellulose cardboard of a polymer mainly cyclic and acyclic diolefins having 5 to 6 Contains carbon atoms, the polymer in situ in the Celluleae ^ appÄ, has been hardened. ORIGINAL 14. Blank according to claim 13, characterized in that the polymer has been incorporated in an amount of 5 to 40 wt.%. 15. Blank according to claim 14, characterized in that it contains 5 to 20 wt.% Of the polymer based on the dry weight of the cellulose cardboard. 16. Cardboard according to claim 14, characterized in that 20 to 40 wt. %. of the polymer, based on the weight of the cellulose paperboard, is incorporated therein. 17. cardboard cartons according to claim 1, characterized in that it has been that the cardboard consists of a cellulose material which is between 5 and 40 wt.% Of the hydrocarbon polymer impregnated based on the untreated weight of the paperboard, wherein the Kohlenstoffpoly- »it in was hardened in situ in the cardboard. 109826/1167 Blank page