WO1992021579A1

WO1992021579A1 - Moisture resistant glass container

Info

Publication number: WO1992021579A1
Application number: PCT/US1992/003413
Authority: WO
Inventors: Wells C. Cunningham; Kenneth L. Crouse; Richard A. Telman
Original assignee: Advanced Glass Treatment Systems
Priority date: 1991-05-31
Filing date: 1992-04-27
Publication date: 1992-12-10
Also published as: AU1799292A

Abstract

A glass container having resistance to strength degradation includes a glass substrate and a layer of a cured reactive coating composition. The composition includes from about 10 weight percent to about 74 weight percent of a monomer having two (meth)acryloyl groups per molecule; from about 5 weight percent to about 50 weight percent of a reactive crosslinking monomer having at least three (meth)acryloyl groups per molecule; from about 20 weight percent to about 70 weight percent of an alkyl monoacrylate monomer; from about 1 weight percent to about 30 weight percent of an organosilane monomer having one or more functional groups capable of reacting with the glass substrate and having a nonhydrolyzable organic functional group capable of reacting with a (meth)acryloyl group and an effective amount of a polymerization initiator compound. A method for increasing the resistance of a glass container to strength degradation includes applying a layer of the above composition and curing the layer by high intensity UV radiation.

Description

MOISTURE RESISTANT GLASS CONTAINER

Technical Field:

The present invention relates to strength

enhancement of glass containers and more particularly to reduction of the detrimental effects of moisture on the strength of glass containers.

Background of the Invention:

It is well known that stress concentration at surface flaws, e.g. nicks, scratches, of a glass container result in a reduction of the strength of the glass container.

It is also known that exposure of a glass container to moisture, e.g. to liquid water or to a humid

environment, results in a gradual degradation of the strength of the container over time. It is believed that chemically adsorbed moisture reacts with siloxane bonds at flaw sites on the container surface to form

hydroxyl groups, thereby further weakening the flaw sites and gradually degrading the strength of the glass container.

Problems associated with reduction in the strength of glass containers due to surface flaws and with time and temperature dependent strength reduction due to gradual moisture driven degradation are particularly acute with regard to glass bottles which contain pressurized contents, e.g. bottles for carbonated beverages.

The immediate reduction in container strength due to surface flaws and the time dependent moisture-driven degradation of container strength are conventionally addressed by overdesign, i.e. by taking projected reductions in container strength into account in the design of the container and producing more massive containers having a correspondingly higher initial theoretical strength to compensate for the projected strength reductions. A method which provides an increase in container strength would allow increased efficiency with regard to both material use, i.e. a reduction in container mass, and container production rate, i.e. other factors being equal, a reduction in container mass allows an increase in container

production rate, primarily due to more rapid cooling of the containers during processing.

Flaw-related strength reduction of glass containers has been addressed in several ways, each typically employed as an adjunct to the above discussed approach of overdesigning the container to compensate for

projected strength losses. Damage prevention coatings, i.e. conventional inorganic "hot end" coatings and organic "cold end" coatings, are used as protective layers to reduce the occurrence of surface flaws. Coatings intended to contain glass fragments from fractured glass bottles are also known.

A method for increasing the strength of glass containers which ostensibly allows a reduction in container mass is described in U.S. Patent Nos.

4,891,241 (Hashimoto et al '241) and 4,961,976

(Hashimoto et al '976). The method of Hashimoto et al comprises applying a reactive coating material to a glass container treated with a silane coupling agent or applying a mixture of the coating material and the silane coupling agent to the glass container and then irradiating the coated container to cure the coating. Hashimoto et al demonstrate an increase in the strength of a container under dry conditions. Hashimoto et al also address short term exposure to "severe

conditions", i.e. hot water and/or hot alkaline water, by introducing an acidic component to the coating material in an attempt to increase adhesion of the coating to the glass surface. However, Hashimoto et al do not address long term moisture-driven degradation of container strength and do not address container

breakage under wet conditions.

While increasing the strength of a glass container should allow a reduction in container mass and a correspondingly increased production rate, it is clear that the problem is not fully addressed by increasing only the short term strength of a dry container and that the time dependent moisture-driven degradation of container strength and the long term strength of the container under humid conditions must be taken into account when attempting to produce lightweight glass containers having a long term strength which exceeds the demands of the particular application of the container by a sufficiently wide margin of safety. Summary of the Invention:

A glass container having improved moisture

resistance is disclosed. The container comprises a glass substrate and a coating layer, comprising the cured reaction product of a reactive liquid coating composition, coating a surface of the substrate. The coating composition comprises:

from about 10 weight percent to about 74 weight percent of a film forming monomer having two

(meth)acryloyl groups per molecule; from about 5 weight percent to about 50 weight percent of a crosslinking monomer having at least three (meth)acryloyl groups per molecule; from about 20 weight percent to about 70 weight percent of an alkyl monoacrylate monomer

selected from the group consisting of ethyl acrylate, propyl acrylate, butyl acrylate and pentyl acrylate; from about 1 weight percent to about 30 weight percent of an organosilane monomer having one or more

functional groups capable of reacting with the glass substrate and having a nonhydrolyzable organic

functional group capable of reacting with a

(meth)acryloyl group; and an effective amount of a polymerization initiator compound.

A process for increasing the humidity resistance of a glass container is disclosed. The process includes applying a layer of the above described reactive liquid coating composition to a surface of the glass container and curing the layer of coating composition.

In a preferred embodiment, the layer of coating composition is cured by irradiating the coated

container with UV radiation at an intensity effective to cure the above described coating composition. An alternative process for increasing the humidity resistance of a glass container is also disclosed. The process includes applying a reactive liquid coating composition to a surface of a glass container at a temperature between 0°C and 50ºC and a relative

humidity between 20% and 75% and curing the coating. The coating composition of the alternative process comprises a film forming monomer having two or more acryloyl or methacryloyl groups per molecule, a

crosslinking monomer having three or more reactive acryloyl or methacrylol groups per molecule, an

organosilane monomer having one or more functional groups capable of reacting with the glass substrate and having a nonhydrolyzable organic functional group capable of reacting with an acryloyl or a methacryloyl group, and a polymerization initiator.

Brief Description of the Drawings:

FIGURE 1 shows a plot of strength enhancement ratio under ambient conditions versus weight percent

monofunctional acrylate monomer.

FIGURE 2 shows a plot of strength enhancement ratio under high humidity conditions versus weight percent monofunctional acrylate monomer.

FIGURE 3 shows a plot of strength enhancement ratio under high humidity conditions versus relative humidity during coating application.

Detailed Description of the Invention:

The glass container of the present invention may comprise any glass container e.g. a glass bottle or a glass jar. In a preferred embodiment, the container of the present invention comprises a bottle for containing a pressurized liquid, e.g. a bottle for containing a carbonated beverage. The glass substrate of the container of the present invention may comprise any silica based glass, e.g. borosilicate, soda-lime-silica or quartz glass.

Preferably, the glass substrate comprises

soda-lime-silica glass.

While the present invention is specifically

described herein with respect to the preferred

embodiment of a glass container, it will be appreciated that the coating composition and process described herein may also be used to increase the resistance of other glass substrates to moisture driven degradation of tensile and/or flexural strength to thereby produce moisture resistant glass articles, e.g. moisture resistant automobile windshields, optical fibers, fluorescent lighting tubes, CRT tubes and glass sheets, other than containers.

The film forming monomer may be any reactive liquid monomer having two (meth)acryloyl groups per molecule. The terminology "(meth)acrylate" as used herein

signifies that either the methacrylate or the acrylate form of the compound may be used interchangeably.

Suitable film forming di(meth) acrylate monomers

include, e.g. di(meth)acrylic esters and

di(meth)acrylamides. Di(meth)acrylic esters of alkyl diols, di(meth)acrylic esters of dicarboxylic acids, di(meth)acrylamides of diamino compounds and mixtures thereof. Specific examples of suitable film forming di(meth)acrylate monomers include ethylene glycol di (meth)acrylate, diethylene glycol di(meth)acrylate, triethyleneglycol di(meth)acrylate, polyethyleneglycol di (meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate tripropyleneglycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1, 3 butanediol di(meth)acrylate, 1, 4 butanediol di(meth)acrylate, 1, 6 hexane diol di(meth)acrylate, bisphenol A di(meth)acrylate, exthoxylated bisphenol A di(meth)acrylates, di(meth)acrylosuccinate, di(meth)acryloadipate, N, N' methylene bis-(meth)acrylamide, N, N' benzilidene

bis-(meth)acrylamide, and N, N' hexamethylene

bis-(meth)acrylamide. Ethylene glycol

di (meth)acrylate, 1, 3 butanediol dimethacrylate, 1, 6 hexanediol dimethacrylate, neopentyl glycol diacrylate and ethoxylated bisphenol A dimethacrylate are

particularly preferred as the film forming monomer.

The coating material of the present invention may include from about 5 weight percent to about 74 weight percent of the film forming monomer. Preferably, the coating material of the present invention includes from about 20 weight percent to about 66 weight percent of the film forming monomer.

The crosslinking monomer may by any reactive liquid monomer having three or more (meth)acryloyl groups per molecule. Suitable crosslinking monomers include, e.g. (meth)acrylic esters of polyhydric alcohols having three or more (meth)acrylic functional groups,

(meth)acrylamides having three or more (meth)acrylic functional groups and mixtures thereof. (Meth)acrylic esters of polyhydric alcohols having an MW less than about 550 are preferred as the crosslinking monomer. Specific examples of suitable crosslinking monomers include trimethylolpropane tri(meth)acrylate,

pentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, ditrimethylolpropane

tetra(meth)acrylate, dipentaerythritol

hexa(meth)acrylate, tri(meth)acrylate of

tris(2-hydroxyethyl) isocyanurate and N, N', N", N"' terephthallylidenetetraacrylamide. Trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate and triacrylate of tris (2-hydroxyethyl) isocyanurate are particularly preferred as the

crosslinking monomer.

The coating material of the present invention may include from about 5 weight percent to about 50 weight percent of the crosslinking monomer. Preferably, the coating material of the present invention includes from about 10 weight percent to about 40 weight percent of the crosslinking monomer.

Increasing the relative amount of acrylate

functional monomer tends to increase the cure speed of the present invention but also tends to decrease the strength of the cured coating under humid conditions. Preferably, a coating composition according to the present invention satisfies a further constraint wherein the combined weight of diacrylate film forming monomer and acrylate crosslinking monomer monoacrylate should not exceed 60% of the total weight of the coating composition. If the combined weight of the difunctional film forming monomer and the

polyfunctional crosslinking monomer monoacrylate exceed 60 % of the coating composition, the excess amount should be selected from the group consisting of

dimethacrylate film forming monomers, methacrylate crosslinking monomers and mixtures thereof.

The alkyl monoacrylate of the present invention is chosen from the group consisting of ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate and mixtures thereof. Butyl acrylate is particularly preferred as the alkyl monoacrylate. As mentioned above, increasing the relative amount of acrylate functional monomer tends to increase cure speed of the coating composition of the present

invention but to decrease the strength of the cured coating produced therefrom. The alkylmonoacrylate monomers of the present invention provide a very significant and unexpected advantage in that they may be included in the coating composition in relatively high amounts, thereby allowing the coating composition to be more rapidly cured, without degrading the

strength of the cured coating composition.

The coating material of the present invention may include from about 20 weight percent to about 70 weight percent of the alkyl monoacrylate monomer. Preferably, the coating material of the present invention includes from about 20 weight percent to about 60 weight percent of the alkyl monoacrylate monomer.

The organosilane coupling agent of the coating composition of the present invention may be any

organosilane monomer having one or more groups capable of reacting with the glass substrate and a

nonhydrolyzable organic functional group capable of undergoing reaction to form a chemical bond with the (meth) acrylate monomers described above. Suitable organosilane coupling agents are those of the general formula:

wherein:

R is a nonhydrolyzable organic functional group which is capable of reacting with a

(meth)acrylorl group, e.g. (meth)acryloxyalkyl, vinyl, allyl, mercaptoalkyl or aminoalkyl, R' is a nonhydrolyzable nonfunctional organic group, e.g. alkyl,

X is a hydroxyl group or hydrolyzable group, e.g. alkoxy, acetoxy, amino or halo, and

n = 0, 1 or 2.

The hydroxyl or hydrolyzable group X is capable of undergoing reaction with, or of undergoing hydrolysis and subsequent reaction with, silanol groups on the glass substrate to chemically bond the organosilane monomer to the surface of the glass substrate. The nonhydrolyzable organic functional group is capable of undergoing reaction with a (meth) acryloyl group of the coating monomers to chemically bond the organosilane monomer within the coating layer. Respective reactions between the hydroxyl or hydrolyzable group X and the glass substrate and between the functional group R and the monomers of the coating composition chemically bond the cured coating layer to the glass substrate.

Preferably, n = 0 or 1, the organic functional group R is a group capable of undergoing free radical polymerization and the hydrolyzable group X is alkoxy. Most preferably, the organic functional group R is (meth)acryloxyalkyl, the nonfunctional organic group R" is methyl or ethyl and the hydrolyzable group X is methoxy or ethoxy. Specific examples of suitable organosilane coupling agents include

3-(meth)acryloxypropyltrimethoxysilane,

3-(meth)acryloxypropyltriethoxysilane,

3-(meth)acryloxypropylmethyldiethoxysilane,

3-(meth)acryloxypropylmethyldichlorosilane,

allyltrimethoxysilane, and vinylmethyldiethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and

p-aminophenyltrimethoxysilane. Methacryloxypropyltrimethoxysilane and

methacryloxypropylmethyldiethoxysilane are particularly preferred as the organosilane.

Mixtures of two or more organosilane coupling agents are also suitable as the organosilane coupling agent.

The coating material of the present invention may include from about 1 weight percent to about 30 weight percent of the organosilane. Preferably, the coating material of the present invention includes from about 5 weight percent to about 20 weight percent of the organosilane.

The polymerization initiator of the coating

composition of the present invention is preferably a photoinitiator which dissociates or decomposes upon exposure to radiation to yield a free radical.

Conventional photosensitizing compounds may be used in combination with the photoinitiator. Photoinitiators which dissociate upon exposure to radiation having a wavelength in the range of 40 nm to 400 nm are

preferred. Suitable photoinitiator compounds include, e.g. benzil, benzophenone, camphorquinone, benzoin n-butyl ether, thioxanthone,

2-hydroxy-2-methyl-1-phenyl-propan-1-one,

1-hydroxycyclohexylphenylketone,

isopropyl thioxanthone, 2,2-dimethoxy-2

phenyl-2-benzyl-2-N-dimethylamino and

1- (4-morpholinophenylbutanone).

Preferred photoinitiators include 2-hydroxy-2-methyl- 1-phenyl-propan-1-one and

1-hydroxycyclohexylphenylketone. Alternatively, the coating material of the present invention may be heat cured by including a thermal initiator, i.e. a compound which decomposes upon heating to yield free radical, in the coating

composition. The thermal initiator may be substituted for the photoinitiator to provide heat curable

composition or may be included in addition to the photoinitiator to provide a composition that may be cured by heat and/or radiation. Suitable thermal initiators include, e.g. 2, 2'-azobis (2, 4

dimethylvaleronitrile), 2-2'-azobis (isobutylnitrile), 2, 2' azobis (methylbutylnitrile), 1,

1'-azobis (cyanocyclohexane) and mixtures thereof. 2, 2 ' azobis (isobutylnitrile) is preferred as the thermal initiator.

The coating material of the present invention may include any effective amount of the polymerization initiator. Preferably, the coating material of the present invention includes from about 5 weight percent to about 20 weight percent of the polymerization initiator.

Alternatively, the polymerization initiator may be omitted from the coating composition if the composition is to be cured by exposure to very high energy

radiation, e.g. an electron beam.

The coating composition of the present invention is made by combining the various components of the

composition and agitating the resultant combination to form a homogenous mixture.

A layer of reactive liquid coating composition is applied to the glass substrate by any convenient method, e.g. dipping, spray coating, flow coating or roll coating. The coating composition may be diluted with a suitable solvent, e.g. methylethylketone,

tetrahydrofuran, and various additives known in the art, e.g. leveling agents, surfactants, may be added to the coating composition in accord with the demands of the particular application method.

Preferably, a layer of reactive liquid coating having a thickness of between 0.3 um and 30 um is applied to a surface of the container. Most

preferably, the layer is between 1 um and 10 um thick.

In the case of a cylindrical container, e.g. a beverage bottle, it is preferred that a solventless layer of the reactive coating composition is applied by roll coating.

Preferably, particularly in the case of glass bottles for containing pressurized liquid, the reactive coating composition is applied to the entire exterior surface of the container. Alternatively, the coating composition may be applied only to those surfaces of the container that are most likely to be damaged, e.g. the circumferential surfaces of a cylindrical container.

Preferably, the coating composition is applied to the container within several hours of heat treating the container as described in copending, coassigned U. S. Application No. 537,507 entitled "Method for Enhancing Strength of A Glass Container and Strength Enhanced Glass Container" by W. C. Cunningham et al.

The '507 application describes a method for

increasing the strength of a glass container by heating the container to a temperature near the annealing temperature of the glass, e.g. above about 500 °C, applying a polymerizable coating composition to the heat treated container, preferably within six hours after the heat treatment, and curing the coating. The coating step may be carried out at any

convenient temperature, e.g. temperatures between about 0°C and about 50°C. Preferably, the coating step is carried out at a temperature between about 15ºC and about 35°C.

The ambient relative humidity during the coating step is an important parameter in the process of the present invention. Preferably, the ambient relative humidity during the coating step is between 20% and 80%. Most preferably, the ambient relative humidity is between 25% and 75%. Controlling the ambient relative humidity within the preferred ranges unexpectedly provides significantly improved strength enhancement performance under high humidity conditions, as

illustrated in Examples 3, 4 and 6 set forth below.

Preferably, the layer of coating composition is cured by exposing the coated container to high

intensity UV radiation. Suitable sources of high intensity UV radiation include, e.g. medium pressure mercury vapor lamps and high pressure mercury vapor lamps.

The speed with which a coating composition may be cured is an important variable with regard to the practical application of the process of the present invention. The speed at which a given composition may be cured depends upon several variables, i.e. coating thickness, ambient O₂ concentration and the intensity of the radiation to which the composition is exposed.

The intensity of the radiation and the duration of the exposure are chosen to fully cure the exterior surface of the coating, i.e. to provide a "tack free" surface at the interface between the coating and the surrounding atmosphere. Preferably, the coated surface of the container is exposed in air to UV radiation having an intensity of greater than about 200 MW/cm² at a wavelength of between about 200 and about 450 nm for a time period between 0.1 second and 100 seconds.

Oxygen has an inhibitory effect on the free radical polymerization reaction and consequently the presence of oxygen tends to decrease the speed of cure. The cure speed of a given composition at a given intensity of radiation may be enhanced by carrying out the curing step in an inert, e.g. N₂ atmosphere. EXAMPLE 1

A series of sample compositions were formulated and tested to demonstrate the effect of increasing the carbon chain length of the alkyl monoacrylate of the composition of the present invention and to compare the results to those obtained using isobornyl acrylate and tetrahydrofurfuryl acrylate as the monoacrylate.

Each composition was applied to microscope slides and cured.

Soda-lime silica microscope slides (nominally 1" × 3" × 1mm) were visually inspected for flaws, e.g.

nicks, scratches. Slides exhibiting visually

detectable flaws were discarded. The thickness of each of the remaining slides was recorded. One side of each of the slides was then abraded with 60 mesh grit at about 80 psi. The abraded slides were then soaked in distilled water for 24 hours, allowed to dry in air at ambient temperature and then heat treated in an oven at about 600°C for 1 hour. The heat treated slides were stored in a dessicator. Slides were removed from the dessicator and curtain coated with 10g of coating formulation. The coated slides were blotted, hung vertically in air for about 10 minutes and blotted a second time.

The coated slides were aligned in a rack and cured by passing the rack under a FUSION SYSTEMS 300 WPI "H bulb" high pressure mercury lamp. The flawed side of each slide was alternately oriented upwardly and downwardly with the successive passes. The slides were subjected to UV radiation at an intensity of about 550

2

mW/cm for 1 second per pass. The number of passes required to obtain a tackfree coating was recorded for each side.

The coated slides were either stored under ambient conditions or soaked in distilled water overnight prior to testing.

The slides were tested in a INSTRON 1122 testing apparatus using a 4 point bend flexural test fixture with a span ratio of 2 and a crosshead speed of 0.2 in/min with the flawed side of the slide in tension.

The strength enhancement (S.E.) ratio is determined by comparing results obtained with coated slides and those obtained with noncoated slides under the same test conditions. "Ambient" strength enhancement values were derived by testing coated slides that had been stored under ambient conditions and tested under ambient conditions. "High Humidity" strength

enhancement values were derived by testing coated slides that had been stored submerged overnight in water and tested wet at room temperature. Five to twenty five samples were tested for each coating composition. Results are expressed as arithmetic averages.

Each of the compositions tested included 10 weight percent crosslinking monomer (trimethylolpropane triacrylate), 14 weight percent organosilane monomer (3-methacryloxypropyltrimeth-oxysilane) and 10 weight percent photoinitiator (2-hydroxy-2-methyl-1-phenylpropan-1-one). The weight percent film forming

monomer, weight percent monoacrylate monomer, number of passes to cure (expressed as flaw side/non flaw side), ambient strength enhancement ratio and high humidity strength enhancement ratio are set forth in TABLE 1 for each coating composition tested.

Results are plotted in FIGURES 1 and 2.

As mentioned above, substitution of a monoacrylate monomer for its methacrylato homolog in a radiation curable coating typically provides a coating composition having a faster cure speed. However, substitution of a monoacrylate monomer for a monomethacrylate monomer in a strength enhancing coating composition typically results in a significant reduction, e.g about 20%, in the high humidity strength enhancement provided by the coating composition.

The results set forth in TABLE 1 and plotted in FIGURES 1 and 2 show that the coating composition of the present invention, which includes an alkylmonoacrylate chosen from the above described group of ethyl acrylate, propyl acrylate, butyl acrylate, peπtyl acrylate and mixtures thereof, unexpectedly provides a rapid cure speed without a corresponding detriment to the high humidity strength enhancement provided by the coating composition. The performance of the coating composition of the present invention allows rapid processing of less massive containers without compromising the strength of the container under very humid or wet conditions.

EXAMPLE 2

A series of sample compositions were formulated and tested to demonstrate the effect of increasing the weight percent of alkylmonoacrylate on the coating composition of the present invention.

Each of the coating compositions were applied to microscope slides, cured and tested according to the procedure set forth in Example 1 above. Each of the compositions included 14 weight percent organosilane monomer (3-methacryloxypropyltrimethoxysilane) and 10 weight percent photoinitiator (2-hydroxy-2-methyl-1-phenylpropan-1-one). The weight percent film forming monomer, weight percent cross linking monomer, weight percent alkyl monoacrylate, number of passes to cure, ambient strength enhancement ratio and high humidity strength enhancement ratio are set forth in TABLE 2 for each of the coating compositions tested.

TABLE 2

CROSSLINKING ALKYL AMBIENT MONOMER^a MONOACRYLATE^c S.E.

(wt %) (wt %) RATIO

FILMFORMIHG NUMBER OF HIGH

FORMUMONOMER^b PASSES HUMIDITY

LATION (wt %) (flaw side/ S.E.

NUMBER second side)

24 10 66 0 5/2 1.S3 1.70

26 10 33 33 3/2 1.62 1.66

27 10 0 66 2/1 1.30 1.17

28 25 51 0 4/2 1.71 1.75

29 25 25.5 25.5 2/2 1.65 1.69

30 25 0 51 1/1 1.09 1.11

31 40 36 0 2/2 1.67 1.76

32 40 18 18 2/1 1.56 1.67

33 40 0 36 1/1 1.09 1.10 a. trimethylolpropane triacrylate

b. 1,3 butanediol dimethacrylate

c. n-butyl acrylate

The results set forth in TABLE 2 demonstrate that the total acrylate monomer included in the coating composition can be apportioned between the crosslinking monomer and the alkyl monoacrylate monomer to maximize the cure speed of the coating formulation without reducing the strength reduction provided by the coating composition. This feature allows the cure speed and the physical properties of the coating composition of the present invention to be adjusted substantially independently. EXAMPLE 3

The performance of a coating composition of the present invention (FORMULATION NO. 34, set forth below) was compared to that of several embodiments of the coating composition described in Hashimoto et al '241 and Hashimoto et al '976.

Formulation No. 34 included (by wt %) :

40 1-3-butylene glycol dimethacrylate;

26 butyl acrylate;

10 trimethylolpropanetriaerylate;

14 3-methacryloxypropyltrimethoxysilane;

10 2 hydroxy-2-methyl-1-phenyl-propan-1-one; and

0.6 siloxane leveling agent.

Comparative formulation 1 (CFl) , corresponding to Example 3 of the Hashimoto et al patents, included (by parts):

60 bisphenol "A" (2-hydroxypropyl) methacrylate;

20 trimethylolpropane triacrylate;

20 tetrahydrofurfuryl acrylate;

7 3-methacryloxypropyltrimethoxysilane;

1 fluorinated copolymer leveling agent; and

4 1-hydroxycyclohexylphenylketone .

Comparative formulation 2 (CF2), corresponding to Example of the Hashimoto et al patents, included (in parts):

6 urethane diacrylate (aliphatic urethane diacrylate 8804, Radcure, mw = 12000);

20 trimethylolpropane triacrylate;

7 3-methylacryIoxypropyltrimethoxysilane;

20 tetrahydrofurfuryl acrylate;

1 fluorinated copolymer leveler; and

4 1-hydroxycyclohexylphenylketone.

Comparative formulation 3 (CF3), corresponding to Example of the Hashimoto et al patents, included (by parts):

40 bisphenol A diacrylate;

10 1,6 hexandiol diacrylate;

10 neopeπtyl glycol diacrylate;

15 trimethylolpropanetriacrylate;

10.9 pentaerythritol acrylate;

5 tetrahydrofurfuryl acrylate;

5 3-methacryloxypropyltrimethoxysilane;

0.1 ACRONAL 4F leveling agent;

4 1-hydroxycyclohexylphenylketone; and

0.055 p-toluene sulfonic acid.

Comparative formulation 4 (CF4), corresponding to Example of the Hashimoto et al patents, included (by parts):

60 πeopentyl glycol diacrylate;

30.9 tetrahydrofurfuryl acrylate;

5 3-methacryloxypropyltrimethoxysilane;

0.1 ACRONAL 4F;

4 1-hydroxycyclohexylphenylketone; and

0.055 p-toluene sulfonic acid. Comparative formulation 5 (CF5), corresponding to Example

69 of the Hashimoto et al patents, included (by parts):

20 dipentaerythritol pentaacrylate;

70.9 dicyclopentenyl acrylate;

5 3-methacryloxypropyltrimethoxysilane;

0.1 ACRONAL 4F leveling agent;

4 1-hydroxycyclohexylphenylketone; and

0.055 p-toluene sulfonic acid.

Comparative formulation 6 (CF6), corresponding to Example

70 of the Hashimoto et al patents, and included (by parts):

5 dipentaerythritol pentaacrylate;

85.9 dicyclopentenyl acrylate;

0.1 3-methacryloxypropyltrimethoxysilane;

4 ACRONAL 4F;

4 1-hydroxycyclohexylphenylketone; and

0.055 p-toluene sulfonic acid.

Each of the coating compositions were diluted to 40 weight percent solids with methyl ethyl ketone and applied to microscope slides, dried in an oven at 60ºC for one minute to evaporate the solvent, cured and then tested under ambient and under high humidity conditions according to the procedure set forth in Example 1 above.

The slides were coated under ambient conditions (about 21ºC and about 23 % relative humidity). The results of testing under ambient conditions, i.e.

number of samples (n) , mean stress at break, standard deviation, percent relative error (% R.E.), number of passes to cure and ambient strength enhancement ratio are set forth in TABLE 3 for each of the coating compositions tested. The slides were tested in a controlled atmosphere (27 - 29°C, 31 - 34 \ R.H.).

TABLE 3

AMBIENT

STD. S E

DEV. RATIO

FORMULAMEAN

TION # STRESS % R.E. PASSES noncoated 12 12895 772 5.99 1.00

34 10 21406 1580 7.38 1.66 5/3

CFl 11 21974 1021 4.65 1.70 2/1

CF2 11 19001 1356 7.14 1.47 2/1

CF3 11 22390 1370 6.12 1.74 2/1

CF4 11 16793 1746 10.40 1.30 3/3

CF5 11 21687 1213 5.59 1.68 2/1

CF6 10 19746 1553 7.86 1.53 2/1

The results of testing under highly humid conditions, i.e. number of samples (n), mean stress at break, standard deviation percent relative error (% R.E.), number of passes to cure and high humidity strength enhancement ratio are set forth in Table 4 for each of the coating compositions tested. The slides were tested wet under controlled conditions (27ºC, approximately 100 % R.H.) after overnight storage m water. TABLE 4

HIGH HUMIDITY

(After overnight storage in water)

STD. S E

n DEV. RATIO

FORMULAMEAN

TION # STRESS % R.E. PASSES noncoated 9 12051 677 5.62 1.00 ┄

34 10 18634 1218 6.54 1.55 5/3

CF1 11 17061 1353 7.93 1.42 2/1

CF2 11 13790 819 5.94 1.14 2/1

CF3 11 14810 907 6.12 1.23 2/1

CF4 11 15926 1266 7.95 1.32 3/3

CF5 11 16330 1651 10.11 1.36 2/1

CF6 11 13380 1824 13.63 1.11 2/1

The results set forth in TABLES 3 and 4 highlight the differences between an embodiment of the coating composition of the present invention (FORMULATION 34) and a number of examples of the coating composition of Hashimoto et al (COMPARATIVE FORMULATIONS 1 - 6) . The compositions of Hashimoto et al tend to provide somewhat faster cure speed than that of the coating composition of the present invention, and provide ambient strength enhancement values ranging from significantly lower than (e.g. CF 4) to somewhat higher than (e.g. CF 3) those provided by the coating compositions of the present invention.

However, the results of TABLE 4 show the high humidity strength enhancement values provided by the comparative formulations is, in all cases, significantly lower than that provided by the coating composition of the present invention. EXAMPLE 4

The performance of the coating composition of the present invention was compared to that of two of the comparative formulations set forth in Example 3.

The testing was conducted according to the procedure set forth in Example 1 and under the same conditions as in Example

3, except for the conditions (19 - 21°C, 13 % R.H.) during tiie coating and curing steps. The results of testing under ambient conditions (27 - 29°C, 31 - 34 % R.H.) are given in TABLE 5.

TABLE 5

AMBIENT

(27 - 29º, 31 - 34% RH)

STD. S E

DEV. RATIO

FORMULAMEAN

TION NO. STRESS % R.E. PASSES noncoated 8 13761 819 5.95 1.00 ┄

34 11 21898 1314 6.00 1.59 5/3

CF1 10 22515 1473 6.54 1.64 2/1

CF5 10 22553 1569 6.96 1.64 2/1

The results of testing under high humidity conditions (wet samples, 27 - 29°C, about 100 % R.H.) are given in TABLE 6.

TABLE 6

HIGH HUMIDITY

(After overnight storage in water)

STD. S E

DIV. RATIO

FORMULAMEAN

TION # STRESS % R.E. PASSES ncoalted 11 11922 1174 9.85 1.00

34 9 17865 1518 8.50 1.50 5/3

CF1 11 12808 828 6.46 1.07 2/1

CF5 10 12744 843 6.61 1.07 2/1

Comparison of the results set forth in TABLES 5 and 6 with those for the corresponding formulation set forth in TABLES 3 and 4 of EXAMPLE 3 reveals that the performance of those coating formulations is strongly and unexpectedly effected by the ambient relative humidity during application of the coating, with higher ambient relative humidity during coating application apparently providing improved strength enhancement performance under wet conditions. It is noteworthy that the performance of the comparative formulations is extremely sensitive to the influence of changes in this process parameter and gave very low, e.g. 1.07, high humidity strength enhancement values when those coatings were applied at the lower ambient relative humidity. EXAMPLE 5

The testing was conducted according to the procedure set forth in Example 1 and according to the procedure set forth in Example 1 and under the same conditions as in Example 4, (19 - 21°C, 13 % RH) except that the coating formulations were not diluted with solvent, i.e. the coating formulations were applied as 100% solids.

The results of testing under ambient conditions (27 - 29°C, 31 - 34 % R.H.) are given in Table 7.

TABLE 7

AMBIENT

STD. S E

DEV. RATIO

FORMULAMEAN

TION # STRESS % R.E. PASSES noncoated 8 13761 819 5.95 1. 00 - - - -

34 11 21783 1136 5.22 1.58 4/2

CF4 11 19312 1267 6.56 1.40 2/2

CF5 11 23236 2070 8.91 1.69 3/2

The results of testing under high humidity conditions (wet samples, 27 - 29°C, about 100 % R.H.) are given in Table 8. TABLE 9

HIGH HUMIDITY

(After overnight storage in water)

STD. S E

DEV. RATIO

FORMULAMEAN

TION # STRESS % R.E. PASSES noncoated 11 11922 1174 9.85 1.00 - - - - 34 9 17138 1335 7.79 1.44 4/2 C^F4 11 14109 1249 8.85 1.18 2/2

CF5 11 12354 673 5.45 1.04 3/2

The results set forth in TABLES 7 and 8 compare well with those set forth in TABLES 5 and 6 of EXAMPLE 4. indicating that the performance of the coating compositions applied neat, i.e. as 100% solids, is equivalent to that of the same composition applied in solution.

EXAMPLE 5

The effect of ambient humidity during coating was further investigated using historical data compiled for a control formulation lacking the alkylmonoacrylate of the composition of the present invention (Formulation No. 35). Formulation No. 35 included (by wt %) : 66 1,3 butylene glycol dimethacrylate;

10 trimethylolpropane triacrylate;

14 3-methacryloxypropyltrimethαxysilane;

10 2-hydroxy-2-methyl-1-phenyl-propan-1-one; and

0.06 siloxane leveling agent

Formulation No. 35 had been coated on slides and tested at under high humidity conditions according to the procedure set forth in Example 1. The high

humidity S.E. ratio so obtained is plotted versus relative humidity during the coating application step in FIGURE 3.

The results shown in FIGURE 3 further define the unexpected relationship between ambient relative humidity during coating application and coating

composition performance under wet conditions discussed in EXAMPLE 4 and indicate that coating application at an ambient relative humidity between about 20% and about 80%, and preferably between about 25% and 75% provides a significant increase in the performance of the coating composition under humid or wet conditions compared to that of the same composition applied under very low, i.e. less than 15% or very high, i.e. greater than 85%, relative humidity.

While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been

described by way of illustrations and not limitations.

What is claimed is:

Claims

CLAIM 1. A glass container having improved moisture resistance,

said container having a burst strength and an impact strength, comprising:

a glass substrate; and

a coating layer coating a surface of the substrate; said coating layer comprising the cured reaction product of a liquid coating composition, said coating composition comprising:

from about 10 weight percent to about 74 weight percent of a reactive film forming monomer having two acryloyl or methacryloyl groups per molecule;

from about 5 weight percent to about 50 weight percent of a crosslinking monomer having at least three acryloyl or methacryloyl groups per molecule; from about 20 weight percent to about 70 weight percent of an alkyl monoacrylate monomer selected from the group consisting of ethyl

acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, and mixtures thereof;

from about 1 weight percent to about 30 weight percent of an organosilane monomer having one or more functional groups capable of reacting with the glass substrate and having a nonhydrolyzable organic functional group capable of reacting with an acryloyl or methacryloyl group; and

an effective amount of a polymerization initiator compound;

said container exhibiting improved resistance to moisture driven degradation of the burst strength and impact strength of the container.

CLAIM 2. The container of Claim 1, wherein the glass substrate comprises a material selected from the group consisting of borosilicate glass, soda-lime-silica glass, and quartz glass.

CLAIM 3. The container of Claim 1, wherein the glass container comprises a bottle for containing a liquid at superatmospheric pressure.

CLAIM 4. The container of Claim 1, wherein the coating layer has a thickness between about 0.1 um and about 20 um.

CLAIM 5. The container of Claim 1, wherein the coating layer is chemically bonded to the surface of the substrate.

CLAIM 6. The container of Claim 2 , wherein the

functional groups capable of reacting with the glass substrate comprise hydroxyl groups or hydrolyzable groups and the hydroxyl groups or hydrolyzable groups are capable of forming chemical bonds with the silanol groups on the surface of the glass substrate.

CLAIM 7. The container of Claim 1, wherein the film forming monomer is selected from the group consisting of ethylene glycol dimethacrylate, 1, 3-butanediol diacrylate, 1, 3-butanediol dimethacrylate, 1, 6 hexanediol dimethacrylate, neopentyl glycol

dimethacrylate, ethoxylated bisphenol A dimethacrylate and mixtures thereof.

CLAIM 8. The container of Claim 1, wherein the

crosslinking monomers is selected from the group consisting of trimethylolpropane trimethacrylate, trimethylolpropanetriacrylate, ditrimethylolpropane tetraacrylate,

triacrylate of tris (2-hydroxyethyl) isocyanurate, pentaerythritol triacrylate and mixtures thereof.

CLAIM 9. The container of Claim 1, wherein the alkyl monoacrylate comprises butyl acrylate.

CLAIM 10. The container of Claim 1, wherein the organosilane monomer is selected from the group

consisting of methacrylox- propyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane,

acryloxypropyltrimethoxysilane,

mercaptopropyltrimethoxysilane and mixtures thereof.

CLAIM 11. The container of Claim 1, wherein the

polymerization initiator is a photoinitiator selected from the group consisting of benzil, benzophenone, camphorquinone, benzoin n-butyl ether, thioxanthone, isopropyl thioxanthone, 2,2-dimethoxy-2-phenyl-2-benzyl-2-N-dimethylamino 1- (4-morpholinophenyl-butanone) 2-hydroxy-2-methyl-1-phenyl-propan-1-one,

1-hydroxycyclohexyl phenylketone, and mixtures

thereof.

CLAIM 12. A process for increasing the humidity resistance of a glass container, comprising:

applying a reactive liquid coating composition to a surface of the glass container, said coating

composition comprising:

from from about 10 weight percent to about 74 weight percent of a film forming monomer having two acryloyl or methacryloyl groups per molecule;

acrylate, propyl acrylate, butyl acrylate, pentyl acrylate and mixtures thereof;

an effective amount of a polymerization initiator compound; and

curing the coating composition.

CLAIM 13. The process of Claim 12, wherein the film forming monomer is selected from the group consisting of ethylene glycol dimethacrylate, 1,

3-butanedioldimethacrylate, 1, 3-butanedioldiacrylate, 1, 6 hexanediol dimethacrylate, neopentyl glycol diacrylate, ethoxylated bisphenol A

dimethacrylate and mixtures thereof.

CLAIM 14. The process of Claim 12, wherein the

crosslinking monomers selected from the group

consisting of trimethylolpropane trimethacrylate, ditrimethylolpropane tetraacrylate, triacrylate of tris (2-hydroxyethyl) isocyanurate, pentaerythritol

triacrylate and mixtures thereof.

CLAIM 15. The process of Claim 12, wherein the alkyl monoacrylate comprises butyl acrylate.

CLAIM 16. The process of Claim 12, wherein the

organosilane monomer is selected from the group

consisting of methacrylox-propyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane,

acryloxypropylmethyldichlorosilane and mixtures thereof

CLAIM 17. The process of Claim 12, wherein the

polymerization initiator is a photoinitiator selected from the group consisting of benzil, benzophenone, camphorquinone, benzoin n-butyl ether, thioxanthone, isopropyl thioxanthone and

2,2-dimethoxy-2 phenyl-2-benzyl-2-N-dimethylamino 1-(4-morpholinophenyl-butanone)

2-hydroxy-2-rnethyl-1-phenyl-propan-1-one,

1-hydroxy-cyclohexylphenylketone, and mixtures thereof.

CLAIM 18. The process of Claim 12, wherein the coating composition is applied at a relative humidity between 20% and 80%.

CLAIM 19. The process of Claim 18, wherein the coating composition is applied at a relative humidity between 20% and 80%.

CLAIM 20. The process of Claim 12, wherein the coating composition is cured by exposure to radiation having a wavelength from 200 nm to 450 nm at an intensity of greater than 200 MW/cm2 for a time period of about

0.1 second to about 100 seconds.

CLAIM 21. The process of Claim 20, wherein the coating composition is cured in air to provide a tack free coating surface.

CLAIM 22. A coated glass container made by the process of Claim 12.

CLAIM 23. A process for increasing the humidity resistance of a glass container, comprising:

applying a reactive liquid coating composition to a surface of a glass container, said coating composition comprising:

a film forming monomer having two acryloyl or methacryloyl groups per molecule;

a crosslinking monomer having at least three acryloyl or methacryloyl groups per molecule;

an organosilane monomer having one or more functional groups capable of reacting with the glass substrate and having a nonhydrolyzable organic functional group capable of reacting with an acryloyl or a methacryloyl group, and

a polymerization initiator,

wherein the coating composition is applied at a relative humidity between 20 % and 80 %; and

curing the coating.

CLAIM 24. The process of Claim 23, wherein the film forming monomer is selected from the group consisting of ethylene glycol dimethacrylate, 1,

3-butanedioldimethacrylate, 1, 3-butanedioldiacrylate, 1, 6 hexanediol dimethacrylate,

neopentyl glycol diacrylate, ethoxylated bisphenol A dimethacrylate and mixtures thereof.

CLAIM 25. The process of Claim 23, wherein the

crosslinking monomers selected from the group

triacrylate and mixtures thereof.

CLAIM 26. The process of Claim 23, wherein the

organosilane monomer is selected from the group

acryloxypropylmethyldichlorosilane and mixtures thereof

CLAIM 27. The process of Claim 23, wherein the

polymerization initiator is a photoinitiator selected from the group consisting of benzil, benzophenone, camphorquinone, benzoin n-butyl ether, thioxanthone, isopropyl thioxanthone and 2,2-dimethory-2 phenyl2-benzyl-2-N-dimethylamino 1- (4-morpholinophenylbutanone) 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxy-cyclocyclohexylphenylketone, and mixtures thereof.

CLAIM 28. The process of Claim 23, wherein the coating composition is applied at a relative humidity between 25% and 75%.

CLAIM 29. The process of Claim 23, wherein the coating composition is cured by exposure radiation having a wavelength from 200 nm to 450 nm at an intensity of greater than 200 MW/cm2 for a time period of about

0.1 second to about 100 seconds.

CLAIM 30. A coated glass container made by the process of Claim 23.

CLAIM 31. The container of claim 1, wherein the coating composition consists essentially of:

an effective amount of a polymerization initiator compound.

CLAIM 32. The process of claim 12, wherein the coating composition consists essentially of:

an effective amount of a polymerization initiator compound.