DE1270209B - Waxy coating compound - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

German class:

Number:
File number:
Registration date:
Display day:

C09d

D 21 II
CO8h

22h-3

55f-11/01

39b-23

November 17, 1960

June 12, 1968

It is known that waxy coating compositions, especially for paper and cardboard, can be improved by adding a mixture of petroleum waxes two different polyalkylenes are added, which differ from one another in terms of their molecular weight differentiate. In this way it is possible to determine the amount of wax mixture required for the coating and thus to reduce the consumption of the coating compound.

Various inconveniences that occur in practice cannot be remedied in this way, e.g. B. the peeling of the wax coating in the form of cords or ribbons on the folded edges of z. B. Packaging cartons or containers for dairy products. Also leave the impact and abrasion resistance in many cases much to be desired.

Surprisingly, it has now been shown that a wax-containing coating composition consisting of a mixture of petroleum waxes and two different polyalkylenes derived from monomeric alkylenes with 2 to 3 carbon atoms in the molecule, which is characterized in that the wax component consists of 40 to 60 percent by weight of one Distillate paraffin wax with a melting point of 50 to 6O ⁰ C, 5 to 20 percent by weight of a heavy distillate paraffin wax with a melting point of 60 to 80 ⁰ C, 10 to 20 percent by weight of a microcrystalline residue wax and 25 to 40 percent by weight of an isoparaffin naphthenic, plastic distillate wax with a Melting point of 40 to 45 ⁰ C and that the coating composition as a polyalkylene component 0.25 to 5 percent by weight of a polyalkylene with a density of 0.860 to 0.910 at 20 ⁰ C and 0.05 to 0.75 percent by weight of a polyalkylene with a density of 0.915 to Contains 0.990 at 20 ⁰ C, in all respects fully satisfied.

The density of the polyalkylenes has no causal relationship with their molecular weight. Polyethylenes of both low and high density can have very different molecular weights in spite of practically the same density values. It was therefore not foreseeable that the combination of polyalkylenes of different densities would make it possible to produce wax-containing coating compositions which meet all requirements, including with regard to economical consumption. The densities of polyalkylenes at 2O ⁰ C are determined by a hydrostatic method in air and kerosene. The monomeric alkylenes from which the polyalkylenes are produced can contain 2 to 3 carbon atoms in the molecule. The through-wax coating compound

Applicant:

Shell Internationale Research Maatschappij N.V., The Hague

Representative:

Dr. E. Jung, patent attorney,

8000 Munich 23, Siegesstr. 26th

Named as inventor:

Robert Gardiner Lutz, Houston, Tex. (V. St. A.)

Claimed priority:
V. St. v. America November 19, 1959
(854013)

Average molecular weights of the polyalkylenes are preferably 1,000 to 12,000, in particular

as 1500 to 6000.

The high density polyalkylene should preferably have a cloud point of about 75 ⁰ C. The cloud point is determined by observing the melt of the polyalkylene at decreasing temperature in the incident light against a black background and noting the appearance of the first cloudiness. The higher the cloud point, the lower the consumption of the coating composition.

The coating compositions according to the invention show a considerable difference between the solidification point (ASTM test D 938) and the melting point (ASTM test D 87). The usual, a single one Wax compositions containing polyethylene show only a small difference or no difference at all between these two values, which also indicates that the wax-containing mass in the cardboard enrobing machine sets particularly quickly, which contributes to reducing the consumption of wax.

The combination of polyalkylenes of high and low density results in coating compounds with properties which cannot be achieved by using one of these polyalkylenes alone. Of the Main advantage gained by the presence of the relatively low density polyalkylene, is the high impact resistance at the temperatures under which the food is stored,

809 559/524

while the main advantage of the relatively high density polyalkylene is the lowering of the Consumption of wax exists, but a good coating remains guaranteed.

The effects of the described combinations of polyalkylenes appear to be of the average Molecular weight of each of the two polyalkylenes to be largely independent. As polyalkylenes Both polyethylene and polypropylene can be used. Table I below contains typical examples of low density polyethylenes and the tables for high polyethylenes Density:

Table I.

Low density polyethylene

template density Cloud point
⁰ C Average
Molecular weight A. 0.880 71 4000 B. 0.880 71 4000 C. 0.890 78 7000 D. 0.910 82 10,000 E. 0.907 79 8000

Table II
High density polyethylene

template density Cloud point a)
⁰ C Average
Molecular weight F. 0.917 > 93 21000 G 0.920 84 2000 H 0.920 82 5000 I. 0.920 83 1500 J 0.920 78 2000 K 0.927 80 2000 L. 0.935 85 2000 M. 0.925 80 1500

35

40

a) 1% polymer in the wax.

The density of the polyethylene in question depends largely on how it is manufactured but also to a large extent by an aftertreatment of the polyethylene, such. B. influenced by irradiation will. The irradiation also causes an improvement in the modulus of elasticity, which then in turn, the properties of the wax-containing coating compositions are favorably influenced. Polypropylene are used in particular because of their better isotactic behavior, so they are preferred to the class of relatively high density polyalkylenes.

The invention is of particular use in the case of wax masses for covering cardboard boxes for dairy products, in which a whole series of strict and interrelated requirements with reference to the physical properties. Ordinary distillate paraffin is far too brittle to be used alone at temperatures such as those used for storing dairy products come into question. It is true that the paraffin can be made microcrystalline with a larger amount Combine wax, which is obtained from lubricating oil residue fractions, but forms one such a mixture is a melt of relatively high viscosity, and in addition, the flexibility of the Wax coating still too low. With the addition of an isoparaffinic-naphthenic soft wax the flexibility at lower temperatures can be increased and the viscosity of the melt reduce.

Even further improvements can be achieved by adding a heavy distillate paraffin wax, in particular with regard to the solidification point and the breaking strength in the event of sudden cooling. in the In the context of the invention, such mixtures of petroleum waxes come into consideration.

The distillate paraffin waxes having a melting point of from 50 to 6O ⁰ C, preferably from 54 to 6O ⁰ C, which form a major component of the coating compositions according to the invention, one normally-lubricating oil fractions distillate obtained from dewaxing waxy from petroleum refining. They mainly consist of normal paraffin waxes and smaller amounts of isoparaffins and naphthenes. The heavy distillate wax having a melting point of 60 to 8O ⁰ C is obtained from the lube oil distillate fraction having the highest boiling point. The microcrystalline residue waxes contain only very small proportions of normal paraffins and they consist predominantly of isoparaffinic and naphthenic waxes having melting points of from about 54 to 71 ⁰ C, typically 60-66 ⁰ C. The above-mentioned plastic distillate waxes with melting points of 40 to 45 ° C are obtained by de-oiling crude distillate waxes, a so-called soft wax initially being obtained which still contains up to 30 percent by weight of oil. This oil is also removed in a known manner at a low temperature.

The production of the new waxy coating compositions presents no difficulties. The individual types of wax are mixed with one another by melting and stirring. The polyalkylenes are preferably incorporated by placing them in a basket or other perforated apparatus and allowing the wax melt to pass through until the polyalkylene is thoroughly dispersed throughout the wax. This is preferably done at a temperature of 55 to 120 ^° C.

In order to prove that the difference in the The density of the polyalkylenes and not a difference in molecular weight is what matters Wax masses with a combination of high and low density polyethylenes with essentially the same average molecular weight, namely about 4,000. The for Wax mass used for this purpose had the following composition:

Distillate paraffin wax,
F. = 58 to 60 ° C 45 ° / o

Heavy distillate wax,
F. = 70 to 71 ° C 10%

Isoparaffinic-naphthenic plastic distillate wax,

F. = 43 ° C 30%

Residual microcrystalline wax,
F. == 63 ° C 15%

Table III

Polyethylene Polyethylene Shock resistance template low density high density (Cracks in cm % % at 7.2 ° C) 1 none none > 75 2 1.0 - 11.3 3 1.20 - 11.3 4th - 0.25 ») 30.8 5 1.0 0.25 Ό 11.8 6th 0.25 ") > 75 7th 1.0 0.25 ") 16.3

(Continuation)

template Wax absorption
the cardboard Cloud point g / m ^{2 0} C 1 31.00 , 2 32.61 71 3 31.00 - 4th 26.35 77 5 26.35 77 6th 23.25 - 7th 23.25 -

a) density 0.920; Molecular weight 5000.

b) density 0.927; Molecular weight 2000.

From the figures in this table it can be seen that the use of a relatively low density polyethylene gave a wax mass of good impact resistance, but the take-up by the normal paperboard of a dairy carton was relatively large. When a relatively high density polyethylene (Sample 4) was used, the impact resistance was greatly reduced while the wax pick-up was improved. However, when the two polyethylenes were combined into a single wax mass (sample 5), both the impact resistance was quite excellent and the wax pick-up remained low. The density of the polyethylene used in this case of low density amounted to 0.880 at 20 ⁰ C.

After it has thus been proven that the beneficial effects on the impact resistance, the wax consumption and the wax absorption has nothing to do with the molecular weight of the polyethylene, further tests were carried out with combinations of polyethylenes of different molecular weights, getting the same degree of improvement in both impact resistance and Wax consumption received as long as both a high density polyethylene and a such low density was represented.

In another comparative experiment, cardboard boxes were coated with wax in a normal coating machine, in one case using an addition of 1.2% of a low-density polyethylene (sample 3 in Table III). Here, 25.4 kg of wax were used to coat 1000 cardboard boxes well. However, if 0.2% of the polyethylene content was replaced by an equal amount of high density polyethylene (0.927), the resulting mixture gave a good coating with a wax consumption of 23.1 kg. 2.2731 cartons were made using the same wax blend as the tests listed in Table III modified with 1% of a low density polyethylene and 0.25% of a high density polyethylene (Sample 7 in Table III). This coating composition had a melting point of about 58 ⁰ C and a solidification temperature of 41 ⁰ C. Table IV below are a number of important properties ίο this mass in the coating of a normal milk carton board having a moisture content of about 5% during processing into cardboard boxes to:

Table IV

Behavior with boxes with one capacity

of 2.271
(Milk cardboard with a moisture content

of 5%)
20th

Consumption in kilograms per 1000 boxes 22.7

Behavior regarding the formation of

Bumps on the surface .. excellent

No cracks through the machine

No cracks in the bottom folds

Initial firmness firm

Firmness firm after 5 days

Bulge in centimeters 0.55

Excellent abrasion resistance at 25 ^{° C}

Behavior when falling 6 times
of the filled cardboard box from a
Height of 17.5 cm at a temperature of 7.2 ° C

No peeled strips

Detached flakes a little

flake

Cracks on the floor in centimeters,
total of 5

From the table above it can be seen that those coated with the wax composition according to the invention Cardboard boxes have excellent properties, as widely used by manufacturers and by Consumers of cartons for dairy products are required.

Claims (2)

Patent claims: 1. Wax-containing coating composition, consisting of a mixture of petroleum waxes and two different polyalylenes which are derived from monomeric alkylenes with 2 to 3 carbon atoms in the molecule, characterized in that the wax component consists of 40 to 60 percent by weight of a distillate paraffin wax with a melting point of 50 to 6O ⁰ C, 5 of a heavy distillate of paraffin wax having a melting point of 60 to 8O ⁰ C, 10 to 20 weight percent of a microcrystalline residue wax and 25 to 40 weight percent consists of a isoparaffinnaphthenischen, plastic distillate wax having a melting point of 40 to 45 ° C to 20 weight percent and that the coating composition as a polyalkylene component contains 0.25 to 5 percent by weight of a polyalkylene having a density of 0.860 7 8 0.910 at 20 ° C and 0.05 to 0.75 percent by weight high density with a cloud point of over contains a polyalkylene having a density from 0.915 to 75 ⁰ C. 0.990 contains at 20 ⁰ C. 2. Wax-containing coating compounds according to claims, publications considered: characterized by being a polyalkylene U.S. Patent No. 2,842,508. 809 559/524 5.68 © Bundesdruckerei Berlin