WO1993003695A1

WO1993003695A1 - Pressure-sensitive labels

Info

Publication number: WO1993003695A1
Application number: PCT/US1991/006310
Authority: WO
Inventors: Susan E. Dollinger
Original assignee: The Dow Chemical Company
Priority date: 1991-08-22
Filing date: 1991-09-04
Publication date: 1993-03-04
Also published as: AU8445291A

Abstract

A pressure sensitive labelstock including a facestock which comprises at least a blend layer of a well-blended combination of a first material selected from the group consisting of low density polyethylene, linear low density polyethylene, ultra low density polyethylene, the copolymers of ethylene and vinyl acetate, acrylate, and acrylic acid comonomers which possess a degree of flexibility and conformability like LDPE, and mixtures of one or more of these materials and a second material selected from the group consisting of polypropylene, an ethylene/propylene copolymer in which propylene is at least about 90 percent by weight, high density polyethylene and mixtures of one or more of these materials.

Description

PRESSURE-SENSITIVE LABELS

The present invention relates generally to plastic labels, and more particularly to pressure- sensitive plastic labels.

The shortcomings of paper labels with respect to tearing, wrinkling, creasing, and the like due to age and moisture, or due to a lack of squeezability or deformability when applied to a deformable substrate, are well known in the labeling industry. As a consequence, a great deal of effort has been devoted in recent years to finding suitable pressure-sensitive plastic label materials.

Much of this effort of late has been directed to the pressure-sensitive labeling of deformable, squeezable containers (usually made from high density polyethylene (HDPE)), and more specifically to achieving a facestock which would have an acceptable degree of contact clarity on at least the predominant unpigmented or lighter-pigmented (e.g., white) of these containers while also acceptably matching the gloss of these containers.

Ideally, a facestock for use on these containers should be squeezable (i.e., should deform and recover as the container is squeezed or flexed without tearing, wrinkling, creasing and the like), die- cuttable, dispensable, dimensionally stable and printable, should provide acceptable contact clarity and gloss match to the container, and should be competitive from a cost standpoint.

The labelstocks currently commercially available for this use include films made from plasticized poly(vinyl chloride) (PVC), and from low and

10 medium density polyethylene homopolymers (LDPE and MDPE, respectively). Vinyl labels are relatively expensive, have dimensional stability problems (exhibit a "halo effect" in exposed adhesive at the periphery of a

,_£- label), and require top-coating for printability, but die-cut and dispense adequately while also providing an acceptable match in gloss to the dominant squeezable unpigmented or white HDPE containers. The primary shortcomings common to the low density and medium 0 density polyethylene materials are that these materials do not dispense well and are generally too glossy compared to the surface of a typical bottle.

The present invention provides an alternative 5 to the vinyl and polyethylene labelstocks. The labelstock of the present invention includes a facestock which is squeezable, dimensionally stable, printable and less expensive than vinyl, and which at the same time offers improved dispensability compared to the 0 polyethylene facestocks, while in at least some embodiments also offering a better match in gloss to a typical unpigmented or white HDPE container than the low and medium density polyethylene facestocks. The present labelstock includes a facestock which comprises at least a blend layer of a well-blended combination of a first material selected from the group consisting of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE), the copolymers of ethylene and vinyl acetate, acrylate, and acrylic acid comonomers which possess a degree of flexibility and conformability like that associated with LDPE, and mixtures of two or more of these materials and a second material selected from the group consisting of polypropylene, an ethylene/propylene random copolymer in which propylene is at least 90 percent by weight, high density polyethylene (HDPE) and mixtures of two or more of these materials, in ratios designed to provide the above- mentioned improvements and benefits.

A labelstock of the present invention includes a pressure-sensitive adhesive-coated facestock on a release-coated liner, with the pressure-sensitive adhesive conventionally positioned between the release coating on the liner and the film facestock. The facestock in a first preferred embodiment consists of a single blend layer of low density polyethylene and polypropylene, with the layer and facestock being from 3.0 to 4.0 mils (0.076 to 0.102 mm) thick.

The low density polyethylene can be any of the commercially-available low density branched materials having a density of less than 0.925 grams per cubic centimeter (25 deg. C), and should comprise from 40 up to 95 percent of the blend layer by weight to maintain the squeezability of the facestock while also being sufficiently stiff to dispense. These low density materials have been commercially produced using free- -it-

radical catalysts under high temperatures and pressures, and contain branched chains of polymerized monomer units pendent from the main polymer "backbone". Further description of these materials may be found, e.g., in United States Patents No. 4,684,576 to Tabor et al. and 4,327,009 to Allen et al. The polypropylene can be from 60 down to 5 percent by weight of the blend layer.

The low density polyethylene is preferably selected to have a refractive index as nearly equal to

10 the polypropylene's refractive index as possible, although a truly optically clear blend would require that the refractive indices of the two materials be virtually identical. Other materials of a conventional

-_t- nature (e.g., processing aids and the like) may be present in the blend layer, or in the layers of the various other embodiments to be described subsequently, but preferably these other materials do not unduly adversely affect the optical quality or other essential 0 properties of the facestocks contemplated herein.

The proportions of the low density polyethylene and polypropylene to be employed in a particular application depend in part on whether a glossier or more 5 of a matte appearance is desired of the facestock and .on whether the film is made by a cast process or by a blown film process. The degree of gloss which is to be desired in a given application depends in turn on how glossy the underlying substrate is. 0

Unpigmented or white pigmented HDPE bottles, which together constitute the largest segment of squeezable bottles, generally have a 60 degree Gardner gloss (per ASTM D-2457) in the rr.-ge of from 5 to 10 percent. Frosty clear vinyl films currently used commercially for the contact-clear pressure-sensitive labeling of these containers have a measured gloss typically no lower than about 35 percent, so that the more highly preferred embodiments described herein are addressed to achieving a gloss value on one side of the facestock or another of 35 percent or lower by ASTM D-

2457 while achieving the property improvements over the previous vinyl and low and medium density facestocks described above. It is to be understood, however, and will be clear from the embodiments and examples provided below that the film facestocks of the present invention may also be tailored to match within commercially acceptable limits the less common glossier squeezable containers, whether made from HDPE or from some other material.

In a film facestock made by a cast film process, an acceptably low gloss value for labeling the typical unpigmented HDPE containers is achieved at polypropylene levels of from around 35 percent to 40 percent by weight and greater. Greater levels can produce lower gloss values, but above 40 weight percent of polypropylene the squeezability of the facestock may not be satisfactory.

It will be understood by those skilled in the art that the upper limit on the polypropylene content of a given label facestock in terms of maintaining acceptable squeezability depends to an extent on the adhesive used with the facestock, but in general terms it will be desirable to use as much polypropylene in the facestock for labeling a typical unpigmented HDPE container as consistent with acceptable squeezability. For cast films, this upper limit appears to be at around 40 weight percent polypropylene, so that a preferred cast facestock will contain from 35 to 40 percent of polypropylene by weight, and more preferably will contain 40 weight percent of polypropylene.

Facestocks made by a blown film process are generally less glossy and have a higher secant modulus (i.e., are stiffer) than a comparable cast film, so that to achieve a suitably matte appearance and a vinyl-like stiffness lesser amounts of polypropylene are required. Preferably, however, the single layer blended facestock of LDPE and polypropylene is made by a cast film process and is composed as described in the preceding paragraph.

In a second embodiment, the facestock has an AB-type two layer construction, with a blended base layer B (the base layer being the layer positioned in contact with the pressure-sensitive adhesive and thus eventually forming the inner layer of the label closest the substrate) being a combination of low density polyethylene and polypropylene, and the skin layer A being low density polyethylene. Preferably, the base layer B will be composed as described in the preceding paragraphs, and will comprise from 70 to 90 percent of the total 3.0 to 4.0 mil (0.076 to 0.102 mm) thickness of the facestock. Preferably, the base layer will be from 75 to 90 percent of the facestock's thickness, and most preferably will be from 80 to 90 percent of the embodiment's thickness.

Comparing the one and two layer constructions described in the preceding paragraphs, the single blend layer embodiment will usually be preferred for applications where more of a matte finish to the facestock is contemplated (e.g., for the labeling of a typical unpigmented HDPE container), because of its greater simplicity of manufacture. The two layer embodiment will be employed where a glossier finish (provided oy the LDPE skin layer) is desired or acceptable, as for example where the unpigmented or white HDPE container has been provided with a glossy cap layer.

In third and fourth preferred embodiments of the facestock, a blend of low density polyethylene with high density polyethylene is employed in a single blend layer (the third embodiment) or with a skin layer of LDPE in a two-layer AB-type layer configuration (the fourth embodiment). It is expected that the third and fourth embodiments will in most applications be slightly less preferred, however, compared to a like-constructed facestock employing a blend layer of LDPE and PP as described above, since to achieve the same low levels of gloss called for in labeling a typical unpigmented or ^• white, matte HDPE container would require.more HDPE than would likely be permitted for maintaining the squeezability of the facestock.

The commercially available high density polyethylenes have a density at 25 deg. C. of greater than 0.940 grams per cubic centimeter. These HDPE's are linear (non-branched) polyethylenes conventionally produced by well-known processes using coordination catalysts of the "Ziegler" type or "Phillips" type or of the "Ziegler-Natta" type, typically at low pressures. Further description of these materials and of the processes for making them can be found, e.g., in the aforementioned United States Patents No. 4,684,576 to Tabor et al. and 4,327,009 to Allen et al. In the third, single blend layer embodiment, the LDPE/HDPE facestock consists of a single blend layer at a thickness of between 3.0 and 4.0 mils (0.076 to 0.102 mm), wherein the low density polyethylene is from 40 to 95 percent by weight of the blend layer and the remainder of the layer is high density polyethylene. Preferably, low density polyethylene is from 60 to 90 percent by weight of the blend layer, and most preferably is from 70 to 80 percent by weight of the blend layer. The low density polyethylene and the high density polyethylene preferably are selected to have refractive indices which differ by as little as possible, although again a truly optically clear blend would require the refractive indices of the blended materials to be virtually identical.

In the fourth embodiment, the facestock has two layers and is of a coextruded AB-type configuration wherein "B" is again the blended base layer and "A" is the outer skin layer. The "A" layer is low density polyethylene, with the "B" layer preferably being composed as in the third embodiment described above. The LDPE skin layer preferably comprises from 5 to 30 percent of the total 3.0 mil to 4.0 mil (0.076 to 0.102 mm) thickness of the facestock, with the blended base layer forming the remainder of the facestock 's thickness. More preferably, the skin layer A is from 10 to 25 percent of the overall thickness of the facestock, and most preferably is from 10 to 20 percent of such thickness.

As in the embodiments based on a blend of LDPE and PP described above, as between the third and fourth preferred embodiments generally the third or single HDPE/LDPE blend layer embodiment will be preferred for lower gloss applications, because of its greater simplicity of manufacture. The fourth, two layer embodiment will be employed where a glossier finish is desired or acceptable.

Other suitable embodiments of the facestock may more generally employ a single blend layer of a well- blended combination of a first material selected from the group consisting of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low

10 density polyethylene (ULDPE), the copolymers of ethylene and vinyl acetate, acrylate, and acrylic acid comonomers which possess a degree of flexibility and conformability like LDPE, and mixtures of two or more of these -₅ materials with a second material selected from the group consisting of polypropylene (PP), an ethylene/propylene random copolymer in which propylene is at least 90 percent by weight, high density polyethylene (HDPE) and mixtures of two or more of these materials. 0

With respect to the possible first materials, the low density polyethylene materials have been described previously. The commercially available or known linear low density polyethylene materials are 5 copolymers of ethylene and minor amounts of alpha, beta- ethylenically unsaturated C3 to C12, especially C4 to C8 alkenes. These materials are generally linear, low density ethylene polymers having alkyl side chains from the alpha-olefin segments, have a density generally of 0 from 0.910 grams per cubic centimeter at 25 deg. C. to

0.925 grams per cubic centimeter, and are produced typically using Ziegler-Natta coordination catalysts by processes such as described in United States Patent No.

4,076,698. Ultra low density polyethylenes (ULDPE), also sometimes called very low density polyethylenes (VLDPE), are linear ethylene copolymers with densities below 0.915 grams per cubic centimeter at 25 deg. C, wherein ethylene has been copolymerized with a higher alpha- olefin such as 1-butene, 1-hexene or 1-octene. A process for making these materials is described, for example, in European Patent Document publication number 120,503- Ultra low density polyethylenes are also commercially 0 available.

Those skilled in the art will recognize that copolymers of ethylene with vinyl acetate (EVA), with acrylate (e.g., EEA, EMA), or with acrylic acid (e.g., _t- EAA, EMAA) comonomers can possess a variety of properties at different comonomer levels, but preferably these copolymers and comonomer levels are selected to possess a similar degree of flexibility and conformability to low density polyethylene. The molecular weight of these materials should conventionally be selected to match viscosities and to thereby optimize film processing and mixing characteristics with the selected second material, with typically suitable copolymers possessing a melt index of from 0.5 grams to 10 grams per 10 minutes.

With respect to the possible second materials, these have already been discussed or require no further explanation.

In still other embodiments, one or more skin layers may be employed in conjunction with a blend layer, for example to provide an outer surface of the facestock and label to help match the gloss of the labeled container or an inner surface of the facestock and label having improved anchorage to the pressure- sensitive adhesive. The one or more skin layers can be selected to permit printing at an outer face of the labels relative to the underlying, labeled substrate, or at an inner face for reverse-printed labels. The one or more skin layers can further be selected to provide other desirable qualities to a label prepared from the labelstock such as chemical or abrasion resistance, barrier, etc. Typically the one or more skin layers will be comprised of materials which have good clarity and low haze, and which further provide the desired qualities at the inner and/or outer surfaces of the label at preferably a low materials cost.

Where the facestock consists of a single blend layer, a well-blended combination of a first and a second material from the groups of materials set forth above is expected to have acceptable contact clarity, although in more general terms it will be preferable to select materials which differ by as little as possible in their refractive indices. The proportions of the materials and the manner of the facestock's manufacture are then selected to achieve a desired stiffness and squeezability as well as a desired degree of glossiness. Where one or more skin layers are employed with a blend layer as a base or core layer, preferably as before the base or core layer is composed as in the single layer embodiment, with the skin layers providing a match to the gloss of a bottle or some other surface property.

The facestocks described herein can be made by both blown and cast processes depending on the requirements of a particular application, although a cast process is generally preferred. The embodiments having a blend layer and one or more skin layers, for example those preferred embodiments having a two-layer AB-type construction, may be made by a lamination process or by coextrusion but are preferably made by a simple coextrusion of the blend and skin layers.

Pressure-sensitive labels may be made from the facestocks of the present invention by conventional methods of making such labels, involving the application of a pressure-sensitive adhesive and a paper or plastic liner to the facestock to form a labelstock, printing and die-cutting the labelstock, and stripping the remaining matrix from the liner to leave a series of spaced-apart pressure-sensitive plastic labels on the liner.

The present invention is further illustrated by the following examples:

Example 1

Blown, monolayer films were prepared on a laboratory-scale 1-inch blown film line from blends in various proportions of The Dow Chemical Company's LDPE 535 grade low density polyethylene (density of 0.9245 grams per cubic centimeter, melt index of 1.9 grams per ten minutes at 190 deg. C, refractive index np=1.51) and Escorene* PP 4193 grade polypropylene (Exxon) (density of 0.90 grams per cc, melt flow rate of 6.8 grams per ten minutes at 230 deg. C, refractive index n_D=1.49) .

These films possessed an average thickness of 3.2 mils (0.081 mm), and were tested for 1 percent secant modulus and for 60 degree gloss per ASTM D-882 and D-2457, respectively, with the gloss at both the inside and outer surfaces of the film being measured. These measurements were also taken of a commercially available frosty clear vinyl facestock for comparison. The results of these tests are shown below in Table 1, and suggest that monolayer blown, 3.2 mil-thick (0.081 mm) LDPE/PP blend films can be made having the stiffness at least of commercial vinyl films at polypropylene contents of 10 weight percent or greater, while the lowest gloss was achieved at the outer surface of a blown 75/25 blend film.

Table 1

60 Deg. Gloss in 60 Peg. Gloss

Composition (wt. 1 Percent Secant Modulus Percent (Inner) (Outer) pet. LDPE/PP) in ksi (kg/mm2) (MD/TD) (MD/TD) (MD/TD)

Example 2

Single-layer, 3.5 mil-thick (0.089 mm) (average thickness) blown films were prepared on a pilot-plant scale blown film line from The Dow Chemical Company's LDPE 681 grade low density polyethylene (density of 0.922 grams per cubic centimeter, melt index of 1.15 grams per 10 minutes, refractive index no=1.51) and from a 75 weight percent/25 weight percent blend of LDPE 681 grade polyethylene with Escorene* PP 4193 grade polypropylene (Exxon) for comparison to a 3.5 mil-thick (0.089 mm) commercial frosty clear vinyl facestock.

Properties measured of these films included their 1 percent secant modulus, yield tensile strength and ultimate tensile strength per ASTM D-882, 60 degree gloss (inside and outside, per ASTM D-2457) and free film shrinkage at 180 degrees Fahrenheit (87.7 deg. C). The free film shrinkage test was conducted by placing an unrestrained 8 inch by 8 inch (20.3 cm. X 20.3 cm.) film sample in a hot air oven at 180 deg. F. (87.7 deg. C) for a period of 8 hours, and then measuring the percent change in dimension in both the machine and transverse directions.

The results of these measurements are reported below in Table 2.

Table 2 shows increased modulus and yield tensile strength values for the LDPE/PP blend film as compared to the LDPE film, slightly improved dimensional stability of the blended film compared to both LDPE and vinyl, and lower gloss values compared to the corresponding 75/25 blend film of Example 1. This last result is believed attributable to the lower melt index and less glossy nature of the unblended LDPE grade of this example compared to the LDPE used in Example 1 , and suggests that the gloss of a blended film can be tailored to more precisely match the gloss of an underlying substrate by selecting particular grades of a resin to be used in the blend film. Example 3

In this Example several films were prepared on a production-scale blown film process. Film A was a single-layer blend of 75 weight percent of The Dow Chemical Company's LDPE 681 grade low density polyethylene (density of 0.922 grams per cubic centimeter, melt index of 1.15 grams per ten minutes at 190 deg. C, refractive index n_D=1.51) and 25 weight percent of Escorene* PP 4193 grade polypropylene (Exxon) .

Film B was an 85/15 blend of the same materials, while Film C was a two-layer coextruded film having a 2.8 mil-thick (0.071 mm) base layer of a 75/25 blend of the same LDPE and PP, with a 0.7 mil-thick (0.018 mm) skin layer of The Dow Chemical Company's LDPE 535 grade low density polyethylene.

Films A, B and C were tested initially for their 1 percent secant modulus (machine and transverse directions) and 60 degree gloss (averaging measurements in machine and transverse directions, respectively, at inner and outer surfaces of film) , with the results reported in Table 3 as follows:

Table 3

1 Percent Secant Modulus 60 Peg. Gloss,

Film in ksi (kg/mm2) (MD/TD) Percent (MD/TP) A (75/25 Blend) 58.6 (41.2V 56.9 (40.0) 96.9/59.4

B (85/15 Blend) 47.0 (33.0V 43.9 (30.9) 110.7/94.4

C (2-layer) 48.2 (33.9)/ 53.0 (37.3) 108.9/93.5 The film facestocks thus prepared then were coated with an acrylic adhesive and cured in a forced- air oven at 160 deg. F. (71.0 deg. C) for one hour. The cured labels were hand-applied to unpigmented 8 oz. (0.24 liter) flame-treated, squeezable high density polyethylene bottles, after which the labeled bottles were placed in the oven to cure for an additional hour. On removal from the oven and subsequent cooling, the bottles were squeezed and flexed fifty times under moderate deformation. The labels showed no wrinkling, cracking or distortion and possessed a contact clarity similar to vinyl's.

Example 4

Monolayer film facestocks were prepared in this Example from a blend of 75 percent by weight of The Dow Chemical Company's LDPE 681 grade of low density polyethylene (density of 0.922 g/cc at 25 deg. C, melt index of 1.15 grams per 10 minutes, no=1.51) and 25 percent by weight of Exxon's Escorene 4193 polypropylene, on pilot-plant scale cast and blown film processes.

The 1 percent secant modulus, yield tensile strength, and ultimate tensile strength properties of each of these facestocks were measured by ASTM D-882 for comparison to one another, and for comparison to the values obtained for a monolayer, 3.5 mil-thick (0.089 mm) facestock prepared on the same pilot-plant scale blown line from the LDPE 681 polyethylene alone, and to a commercial frosty clear vinyl facestock. Sixty degree gloss values at both the inner and outer surfaces of the various films were obtained as well (by ASTM D-2457) for further comparison. The values obtained from these tests on the blended films are reported below in Table 4, with the values for the low density and vinyl films being taken from Example 2 above for ready comparison.

Table 4

Property Cast Blown LDPE Vinyl

1 Percent Secant

Modulus, ksi 42.0 (29.5)/ 34.7 66.3 (46.6)/ 59.8 28.4 (20.0)/ 32.7 46.2 (32.5)/ 44.3

(kg mm2) (MD TD) (24.4) (42.0) (23.0) (31.1)

Yield Tensile

Strength, psi 1898 (1.334)/ 2570 (1.807)/ 1,613 (1.134)/ 1,888 (1.327)/

(kg/mm2) (MP TP) 1596 (1.122) 2390 (1.680) 1,602 (1.126) 1,893 (1.331)

Ultimate Tensile

Strength, psi 4438 (3.120)/ 4204 (2.956)/ 3,347 (2.353)/ 2,536 (1.783)/

(kg/mm2)(MP/TP) 2833 (1.992) 3116 (2.191) 3,100 (2.179) 2,127 (1.495)

60 Deg. Gloss,

Percent (Inner) 90.2/43.5 74.2/44.7 90.3/86.6 67/62

60 Deg. Gloss,

Percent (Outer) 89.7/45.1 65.5/35.7 82.9/67.8 38/32

The results in Table 4 show an improvement in the 1 percent secant modulus properties of even cast blended films over that possible with a blown LDPE facestock. Table 4 further shows that a film made by a cast process as opposed to a blown process is less stiff and possesses less tensile strength, while being glossier in general.

Example 5

A 2.2 mil-thick (0.056 mm) monolayer film facestock was prepared for this Example on a pilot plant scale cast film line from a blend of equal parts by weight of The Dow Chemical Company's LDPE 535 grade low density polyethylene and of E.I. DuPont de Nemours & Company's Alathon 7840 grade high density polyethylene (density of 0.960 g/cc, melt index of 6.0 grams per 10 minutes at 190 deg. C, refractive index of 1.54). The facestock was tested according to ASTM D-882 for its 1 percent secant modulus in the machine and transverse directions, and its yield tensile strength and ultimate tensile strength in both machine and transverse directions. Sixty degree gloss values were obtained according to ASTM D-2457 at the inner and outer surfaces of the film in the machine and transverse directions (the inner surface of the film in this and other cast roll examples being understood as signifying the face of the film in contact with the chill roll). The results of these tests are shown in Table 5, and demonstrate a 1 percent secant modulus similar to vinyl's:

Table 5

1 Percent Secant Modulus, ksi

(kg/mm2) (MD/TD) 54.4 (38.2V62.6 (44.0)

Yield Tensile Strength, psi (kg/mm2) (MD/TD) 2233 (1.570)/2387 (1.678)

Ultimate Tensile Strength, psi

(kg/mm2) (MD TD) 3312 (2.329)/1800 (1.266)

60 Deg. Gloss, Inner (MD/TD) 124.9/123.6

60 Deg. Gloss, Outer (MD/TD) 122.6/119.5

Table 5 also shows the greater gloss associated with blended films of LDPE and HDPE compared with the blended LDPE/PP films of earlier examples.

Example 6

For this Example a 3.5 mil-thick (0.089 mm), monolayer film facestock was made on a pilot plant scale blown film process from a blend of 60 percent by weight of The Dow Chemical Company's LDPE 535 grade low density polyethylene and 40 percent by weight of a high density polyethylene (density of 0.960 g/cc, melt index of 5.5 grams per 10 minutes at 190 deg. C, refractive index of ^~

1.54). This facestock was also tested for 1 percent secant modulus, yield tensile strength, ultimate tensile strength and 60 degree gloss in the manner of the previous example, with the results shown in Table 6 as ₀ follows:

Table 6

1 Percent Secant Modulus, ksi

(kg/mm2) (MD/TD) 75.2 (52.9V77.1 (54.2) 5 Yield Tensile Strength, psi (kg mm2)

(MD/TD) 2733 (1.92D/3188 (2.241)

Ultimate Tensile Strength, psi

(kg mm2) (MD/TD) 2345 (1.649V1867 (1.313)

60 Deg. Gloss, Inner (MD/TP) 85/88 0

60 Peg. Gloss, Outer (MP/TP) 82/84

5 Tables 5 and 6 taken together show again that blown films generally may be expected in a LDPE/HDPE system also to possess a higher 1 percent secant modulus/stiffness while being considerably less glossy, and further that HDPE/LDPE film facestocks are glossier than PP/LDPE facestocks at comparable loadings of the HDPE and PP.

Example 7

A series of monolayer film facestocks were prepared on a research- or laboratory-scale cast film process from blends of various proportions by weight of The Dow Chemical Company's LDPE 6811 grade low density polyethylene (density of 0.922 grams per cubic centimeter, melt index of 1.15 grams per ten minutes at 190 deg. C, refractive index n_D=1.51) and of Exxon's Escorene 4193 polypropylene. Each of these film facestocks was tested as per previous examples for 1 percent secant modulus in the machine and transverse directions and for 60 degree gloss at the inner 0 (adjacent the chill roll) and outer surfaces of a respective facestock in the machine and transverse directions. The results of these tests are shown below in Table 7.

Table 7

Composition Average _Λ. , , — : — ^~—r- 60 Degree Gloss, 60 Degree Gloss.

(Wt. % m T_ιhic"1kness, i .n — Mo -rd—ul.us in — k —si — Inner ^B.- P-zercen -t* O -.u ,t,e *r. P _πercen rt¹

LDPE/Wt.% PP) mils ⁽mm⁾ (MWYD₎ ⁽MD/TD) ⁽MD/TD⁾

Table 7 shows that gloss values comparable to or lower than those seen in the commercial vinyl facestocks may be obtained with PP contents of about 35 percent by weight and greater, while achieving also a similar or greater degree of stiffness as indicated by the 1 percent secant modulus of the films.

The film facestocks thus prepared and tested were then coated with an acrylic adhesive and cured in a forced-air oven at 160 deg. F. (71.0 deg. C.) for one hour. The cured labels were hand-applied to unpigmented 8 oz. (0.24 liter) flame-treated, squeezable high density polyethylene bottles, after which the labeled bottles were placed in the oven to cure for an additional hour. On removal from the oven and subsequent cooling, the bottles were squeezed and flexed fifty times under moderate deformation. The labels at the 30 percent and 35 percent polypropylene loadings showed no wrinkling, cracking or distortion and possessed a contact clarity similar to vinyl's, while the labels prepared from a 40 weight percent facestock began to show some signs of wrinkling. The labels prepared from the 50 and 60 weight percent polypropylene facestocks wrinkled.

While preferred embodiments of the labelstocks and labels of the present invention have been described and exemplified above, it will be understood that numerous changes may be made to these embodiments which do not depart in scope or spirit from the present invention as defined more particularly by the claims below. For example, while the present invention is more particularly directed to the development of contact- clear squeezable pressure-sensitive plastic labels for squeezable or deformable substrates, it will be readily apparent that the labels of the present invention could also be employed on non-deformable substrates and/or could be pigmented or filled to act as a conventional pressure-sensitive paper replacement.

Claims

Claims:

1. A pressure sensitive labelstock including:

(a) a facestock which comprises at least a blend layer of a well-blended combination of

(i) a first material selected from the group consisting of low density polyethylene, linear low density polyethylene, ultra low density polyethylene, the copolymers of ethylene and vinyl acetate, acrylate, and acrylic acid comonomers which possess a degree of flexibility and conformability like LDPE, and mixtures of one or more of these materials; and

(ii) a second material selected from the group consisting of polypropylene, an ethylene/propylene copolymer in which propylene is at least about 90 percent by weight, high density polyethylene and mixtures of one or more of these materials;

(b) a liner; and

(c) a pressure-sensitive adhesive joining the liner and facestock.

2. A pressure sensitive labelstock as defined in Claim 1 , wherein the facestock is a single blend layer, from 3-0 to 4.0 mils (0.076 to 0.089 mm) thick, of from 40 to 95 percent by weight of low density polyethylene and from 60 to 5 percent by weight of polypropylene.

3. A pressure sensitive labelstock as defined in Claim 2, wherein the facestock is made by a cast film process and consists of a blend of from 35 percent by 0 weight to 40 percent by weight of polypropylene and the balance of low density polyethylene.

4. A pressure sensitive labelstock as defined in Claim 3» wherein the facestock is 40 percent by r- weight of polypropylene, the balance being low density polyethylene.

5. A pressure sensitive labelstock as defined in Claim 1, wherein the facestock is a single blend _Q layer, from 3.0 to 4.0 mils (0.076 to 0.089 mm) thick, of from 40 to 95 percent by weight of low density polyethylene and from 60 to 5 percent by weight of high density polyethylene.

5 6. A pressure sensitive labelstock as defined in Claim 5, wherein the facestock is from 60 to 90 percent by weight of low density polyethylene and from 40 to 10 percent by weight of high density polyethylene.

7. A pressure sensitive labelstock as defined in Claim 6, wherein the facestock is from 70 to 80 percent by weight of low density polyethylene and from 20 to 10 percent by weight of high density polyethylene.

8. A pressure sensitive labelstock as defined in Claim 1 , wherein the facestock comprises at least one skin layer and a blend layer which consists of a well- blended combination of (i) a first material selected from the group consisting of low density polyethylene, linear low density polyethylene, ultra low density polyethylene, the copolymers of ethylene and vinyl acetate, acrylate, and acrylic acid comonomers which possess a degree of flexibility and conformability like LDPE, and mixtures of one or more of these materials and (ii) a second material selected from the group consisting of polypropylene, an ethylene/propylene copolymer in which propylene is at least about 90 percent by weight, high density polyethylene and mixtures of one or more of these materials.

9. A pressure sensitive labelstock as defined in Claim 8, wherein the facestock is from 3-0 to 4.0 mils (0.076 to 0.089 mm) thick and consists of a base layer which is from 70 to 90 percent of the facestock's total thickness and which consists of a blend of from 40 to 95 percent by weight of low density polyethylene with from 60 to 5 percent by weight of polypropylene, and a printable skin layer which is from 30 to 10 percent of the facestock's thickness and which consists of low density polyethylene.

10. A pressure sensitive labelstock as defined in Claim 9, wherein the base layer is from 75 to 90 percent of the facestock's 3.0 to 4.0 mil thickness, and the printable skin layer is from 25 to 10 percent of the facestock's thickness.

11. A pressure sensitive labelstock as defined in Claim 10, wherein the base layer is from 80 to 90 percent of the facestock's 3.0 to 4.0 mil (0.076 to 0.089 mm) thickness, and the printable skin layer is from 20 to 10 percent of the facestock's thickness.

12. A pressure sensitive labelstock as defined in Claim 8, wherein the facestock is from 3.0 to 4.0 mils (0.076 to 0.089 mm) thick and consists of a base layer which is from 70 to 95 percent of the facestock's total thickness and which consists of a blend of from 40 to 95 percent by weight of low density polyethylene with from 60 to 5 percent by weight of high density polyethylene, and a printable skin layer which is from

30 to 5 percent of the facestock's thickness and which consists of low density polyethylene.

13. A pressure sensitive labelstock as defined in Claim 12, wherein the base layer is from 75 to 90 percent of the facestock's 3.0 to 4.0 mil (0.076 to 0.089 mm) thickness, and the printable skin layer is from 25 to 10 percent of the facestock's thickness.

14. A pressure sensitive labelstock as defined in Claim 13, wherein the base layer is from 80 to 90 percent of the facestock's 3.0 to 4.0 mil (0.076 to 0.089 mm) thickness, and the printable skin layer is from 20 to 10 percent of the facestock's thickness.

15. A pressure-sensitive label formed from the labelstock of any of Claims 1-14.

16. A squeezable substrate to which has been attached a label formed from the pressure sensitive labelstock of any of Claims 1-14.