WO1992000349A1

WO1992000349A1 - Plasticized polyvinyl butyral and sheet formed thereof

Info

Publication number: WO1992000349A1
Application number: PCT/US1991/004402
Authority: WO
Inventors: Ildefonso Luis Gomez; Roland Joseph Tetreault
Original assignee: Monsanto Company
Priority date: 1990-07-02
Filing date: 1991-06-21
Publication date: 1992-01-09
Also published as: AU8239191A; MX9100041A

Abstract

A composition and a sheet of such composition for laminated glazings comprising polyvinyl butyral resin plasticized with a mixture of a) dioctyl adipate (DOA) and b) an exudation-reducing amount of i) one or more monoesters of a glycol and a C16 to C20 unsaturated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of i) and ii), the ratio of i) to ii) in the mixture of iii) being between about 1:1 to 5:1. On a weight basis the plasticizer mixture is about 65-95 %, preferably 70-90 %, DOA and 35-5 %, preferably 30-10 % of b).

Description

P ASTICIZED POLYVTNYL BUTYRAL AND SHEET FORMED THEREOF

BACKGROUND OF THE INVENTION This invention relates to plasticized poly- vinyl butyral resin and sheet formed therefrom and more particularly to improving the performance of dioctyl adipate as the plasticizer therein.

Polyvinyl butyral resin as sheet for use as an optically transparent, impact-dissipating inter- layer in laminated safety glazings is well known.

Since the glass transition temperature of unplasti- cized polyvinyl butyral resin is too high for use in these impact-dissipating applications, it is also known to plasticize such resin to reduce such temper- ature to a useful range.

Octanol, and particularly 2-ethyl hexanol which is abundantly commercially available, when esterified with adipic acid forms dioctyl adipate (DOA) ester which has been widely used to plasticize polyvinyl chloride. Unfortunately, as particularly noted in examples 42-45 of U.S. 3,884,865, DOA is an ineffective plasticizer of polyvinyl butyral resin of the type used with glass in laminated glazings. Such resin for use as sheet in safety glazings is composed of polyvinyl alcohol partially condensed with butyral- dehyde so as to contain from 15% to 25%, preferably, 18 to 24% by weight, unreacted hydroxyl groups. This material is commonly called polyvinyl butyral or more exactly "partial polyvinyl butyral", hereinafter sometimes abbreviated as PVB.

It would be desirable to render DOA effec¬ tive as a plasticizer for PVB resin. SUMMARY OF THE INVENTION Now, improvements have been made in plasti- cizers for PVB resin which mitigate shortcomings of the prior art. Accordingly, a principal object of this invention is to improve the effectiveness of DOA as a plasticizer for PVB resin.

Another object is to provide an improved DOA plasticizer composition for PVB resin. Other objects will in part be obvious from the following description and claims.

These and other objects are accomplished by providing a method of improving the effectiveness of dioctyl adipate as a plasticizer for partial polyvinyl butyral resin which comprises incorporating into a mixture of dioctyl adipate and the resin, an exudation- reducing amount of a composition of i) one or more monoesters of a glycol and a C_lβ to C₂_ unsaturated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of said one or more monoesters and castor oil, the ratio of one or more monoesters to castor oil in the mixture of iii) being between about 1:1 to about 5:1.

Also provided is a formulation of PVB resin plasticized with a mixture of a) dioctyl adipate and b) an exudation-reducing amount of a composition of i) one or more monoesters of a glycol and a C₁₆ to C_2Q unsaturated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of said one or more monoesters and castor oil, the ratio of one or more monoesters to castor oil in the mixture of iii) being between about 1:1 to about 5:1.

Further provided is a sheet of PVB resin plasticized with a mixture of a) dioctyl adipate and b) an exudation-reducing amount of a composition of i) one or more monoesters of a glycol and a C1-6, to C20_/~ unsaturated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of said one or more monoesters and castor oil, the ratio of one or more monoesters to castor oil in the mixture of iii) being between about 1:1 to about 5:1.

DETAILED DESCRIPTION OF THE INVENTION The major dioctyl adipate component of the plasticizer blend of the invention comprises one or more dioctyl esters of adipic acid. The octyl moiety of the ester can be linear (i.e. n-octyl) or any form of a branched octyl moiety including mixtures of linear and branched octyl moieties. Pure (100%) di(2-ethyl hexyl) adipate is preferred.

The major (more than 50 weight %) adipate component of the plasticizer blend of the invention is prepared by esterifying adipic acid and one or more linear or branched octyl alcohols according to syn- thesis procedures well known to those skilled in the art. Depending on alcohols chosen, the resulting product is a pure or mixed adipate. Ethyl hexyl alcohol is preferred which, after esterification, provides pure di(2-ethyl hexyl) adipate. Dioctyl adipate is also available commer¬ cially from Akzo; Ashland Chemical Co.; Exxon Chemical Co.; Hϋls-America and Monsanto Co.

The minor component of the plasticizer blend of the invention is described in U.S. 4,563,296, Col. 3, lines 11-59. More particularly, such minor component is a composition of: i) one or more mono¬ esters of a glycol and a C.,, to C_2Q unsaturated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of said one or more monoesters and castor oil. The mixture iii) of components i) and ii) is preferred. Component i) comprises a monoester of a glycol and a c₁₆ to C_{2 unsaturatβd fatty acid having} a hydroxyl group attached to the acid molecule. The preferred monoester is propylene glycol 1,2 mono- ricinoleate. Acids which can be used to form the monoester have 10 to 20 carbon atoms and include, in addition to ricinoleic acid (12-hydroxyoleic acid), other hydroxy-oleic acids with the hydroxyl groups located other than on the "12" carbon atom such as 6-,8-,14-, or 16-hydroxy-oleic acid, 12-hydroxyelaidic acid and acids with the same empirical formula with the hydroxyl located other than on the "12" atom. Included also are the corresponding variations of 12-hydroxy-hexodec-9-enoic acid and 12-hydroxy-eicos- 9-enoic acid. A single acid may provide all the esterifying acid groups but usually a mixture of unsaturated esterifying acids are used provided the esterifying acids together provide at least one unsaturation and one hydroxyl groups per molecule of monoester.

Component ii) as castor oil is a triglyceride ester of unsaturated fatty acids. It comprises a mixture of esters of glycerol with the following acids, (the figures in parentheses being the approximate weight % of ester formed from that acid): ricinoleic acid (89.5%), oleic acid (3.0%), linoleic acid (4.2%), and dihydroxy-stearic acid (0.7%).

When using the preferred mixture iii) of components i) and ii) as the minor constituent of the plasticizer blend, the weight proportion of monoester i) to castor oil ii) should be between about 1:1 to about 5:1. It is preferred that the monoester be the major component of this minor constituent mixture and therefore be present in an amount greater than the castor oil. The most preferred proportion of monoester to castor oil is 2.3:1. The monoesters are commercially available from CasChem Inc., Bayonne, N.J., 07002 under the registered trademark Flexricin. The various grades of each used in the Examples following are identified in the footnotes to Table 1. Castor oil is likewise available from this firm.

The exudation-reducing amount of the minor component in the plasticizer blend will vary depending on the particular property of the sheet formed of the formulation is desired to be improved. Based on the total weight of plasticizer blend, the amount of monoester or castor oil or combined monoester/castor oil constituent is always less than the primary DOA component. The preferred weight ratio of the DOA major component to the minor monoester or castor oil or mixed monoester/castor oil component is between about 5:1 to 1.9:1 and preferably about 3:1. On a weight basis, a preferred plasticizer composition is about 65-95%, preferably 70-90% DOA and correspondingly 35-5%, preferably 30-10% minor component.

The total amount of plasticizer in the formulation to form the interlayer sheet depends on the specific PVB resin and the properties desired in the sheet application. Generally between 15 to 50, preferably 25 to 40 parts total plasticizer per 100 parts of PVB resin (PHR) is used.

The PVB resin employed has a weight average molecular weight greater than 100,000, preferably from about 200,000 to 300,000, as measured by size exclusion chromatography using low angle laser light scattering. Such PVB comprises, on a weight basis, 15 to 25%, preferably 18 to 24% hydroxyl groups calculated as polyvinyl alcohol (PVOH); 0 to 10%, preferably 0 to 3% residual ester groups, calculated as polyvinyl ester, e.g. acetate, with the balance being butyralde- hyde acetal. PVB resin is produced by known aqueous or solvent acetalization processes wherein PVOH is reacted with butyraldehyde in the presence of acid catalyst to produce PVB, followed by neutralization of the catalyst, separation, stabilization and drying of the PVB resin. It is commercially available from Monsanto Company as Butvar® resin.

Plasticized PVB as interlayer sheet at a thickness of about 0.13 to 1.3 mm is formed by mixing the PVB resin and plasticizer (and optional, additional, well-known property-enhancing additives) and then extruding the formulation through a sheeting die, i.e. forcing molten, plasticized PVB through a horizontally long vertically narrow die opening substantially conforming in length and width to that of the sheet being formed, or by casting molten polymer issuing from an extrusion die onto a specially prepared surface of a die roll in close proximity to the die exit to impart desired surface characteristics to one side of the molten polymer. When the roll surface has minute peaks and valleys, sheet formed of polymer cast thereon will have a rough surface on the side con¬ tacting the roll which generally conforms respectively to such valleys and peaks. A rough surface on the other side can be provided by the design of the die opening through which the extrudate passes. Such a die opening configuration is more particularly shown in Fig. 4 of U.S. No. 4,281,980. Alternative known techniques of producing a rough surface on one or both sides of an extruding sheet involve the specification and control of one or more of the following: polymer molecular weight distribution, water content and temperature of the melt. Such techniques are dis¬ closed in U.S. Nos. 2,904,844; 2,909,810; 3,994,654; 4,575,540 and European Patent No. 0185,863. As is known, this rough surface on the interlayer is temp¬ orary to facilitate deairing during laminating after which it is melted smooth from the elevated tempera¬ ture and pressure associated with autoclaving. In addition to plasticizer, sheet of the invention may contain other additives such as dyes, pigments, ultraviolet light stabilizers, antioxidants, adhesion control salts and the like.

The following tests were used to obtain results listed in the Examples.

A) Compatibility

Exudation Test - Plasticizer and PVB resin compatibility as reflected in long term inter¬ layer edge stability in a laminate is simulated by this laboratory test. Various amounts of plasticizer and PVB resin were blended for 7 min at 150°C in a Brabender mixer equipped with sigma blades turning at 50 rpm. Using a heated hydraulic press (149°C, 5.5 MPa for 5 min), the resulting plasticized PVB resin was pressed into 0.76 mm thick sheets which are representative of interlayer usable with glass in laminated glazings. -The sheets were cut into 17:5 x 38 mm samples, dried for 5 days in a desiccator and weighed to get dry weight. These samples were then placed in a wet desiccator (enclosed chamber con¬ taining water) for seven days. Each sample was then sandwiched between layers of absorbing cardboard, placed between jaws of a clamp being forced together at a pressure of 1.6 MPa The clamped samples were placed in a wet desiccator for 10 days. The clamps were removed, the samples washed with warm water to remove residual cardboard, dried five days in a dry desiccator and again weighed. The weight difference in gm/m 2 of surface area i.s plasti.ci.zer exudation weight loss. The control plasticizer was 100% di-n- hexyl adipate (DHA) which is used extensively in commercial PVB sheet. B) Impact Resistance

1) Mean Penetration Velocity-30.5 x 30.5 cm x 0.76 mm two ply glass laminates were pre¬ pared using the laminating conditions recited above and were individually horizontally positioned in a support frame. While at a constant laminate temper¬ ature of -17°C, a 2.27 kg spherical ball was dropped from a designated height onto the center of the laminate. Two spaced magnetic coils were positioned beneath the test laminate. After penetrating a laminate, the ball sequentially passed through magnetic fields created by the coils and as these fields were disturbed the top coil triggered a timer "on" switch while the bottom coil turned it off. Knowing the time to traverse the distance between coils permits calculating ball velocity. This residual ball velocity is related to energy absorbed by the laminate and absorbed energy in miles per hour (mph) equals laminate Mean Penetration Velocity (MPV). Measured MPV is the average of multiple ball drops from different heights.

2) Pummel Adhesion measures inter¬ layer adhesion to glass. Two ply glass laminates prepared as recited above for the MPV test were conditioned to -17°C and manually pummeled with a 1 pound (454g) hammer to break the glass. All broken glass unadhered to the PVB layer was then removed. The amount of glass left adhered to the interlayer is visually compared with a set of standards of known pummel scale, the higher the number of the standard, the more glass remaining adhered to the interlayer - i.e. at a pummel of zero, no glass at all is left whereas at a pummel of 10, 100% of the interlayer surface is adhered to the glass. Desirable impact dissipation occurs at a pummel adhesion value of 3 to 7, preferably 4 to 6. At less than 3 too much glass is lost whereas at more than 7 adhesion is generally too high and shock absorption is poor. C) Laminate Color

Yellowness Index - Two ply glass lamin- ates with sample interlayer of 6.3 mm thickness were prepared as recited above. Yellowness Index (YI) was measured using a Hunter D54 Spectrophotometer.

The invention is further described with reference to the following Examples which are not intended to limit or restrict the invention. Unless otherwise indicated, all quantities are expressed in weight.

EXAMPLES 1-12 PVB resin for admixture with the plasticizer blend had less than 3% residual acetate groups and a vinyl alcohol content of 18.2%. Exudation test results follow in Table 1. In all of Examples 1-11 the primary plasticizer was pure di(2-ethyl hexyl) adipate and, where used, the minor constituent, referred to as "coplasticizer" was the preferred monoester/castor oil mixture of 70% propylene glycol monoricinoleate, 30% castor oil. PHR means parts total plasticizer per 100 parts PVB resin. % reduc¬ tion refers to the decrease in exudation weight loss with coplasticizer over the control at equivalent loadings in the resin.

Control Example 12 contained 100% DHA.

TABLE 1

Example Total Plast. Coplasticizer Exudation Loss % Reduction

(PHR) % Ratio-Primary/ g/m² coplasticizer

Exs. 2, 4, 6, 8 and 9-11 illustrate signifi¬ cant reductions (in certain cases at least 15%, e.g. from 19 to 53%) in total plasticizer exudation weight loss when the preferred minor coplasticizer mixture constituent of the invention is present in a plasti¬ cizer blend with DOA. The control Examples at 100% DOA confirm the unacceptable performance of DOA as a sole plasticizer in PVB resin. At 100%, sufficient DOA cannot be retained in the PVB resin to provide a glass transition temperature low enough for the plasticized mixture to be effectively used as an interlayer to absorb impact.

EXAMPLES 13-17 These illustrate alternative coplasticizer compositions in a blend with DOA. Coplasticizer content in the plasticizer blend in each case was 18% providing a 4.6:1 ratio of primary/coplasticizer. The PVB resin was the same as in Examples 1-12. Results follow in Table 2. Castor oil is abbreviated "CO.".

'Flex 9 is propylene glycol lonoricinoleate ²Flex 15 is ethylene glycol aonoricinoleate

Contains 89.5 triglyceride ■onoricinoleate

EXAMPLES 18-20 These illustrate interlayer impact and color performance in comparison with a DHA control. Examples

18, 19 were the plasticizer blend compositions of

Examples 9, 11 above; control Example 20 was 100% DHA at 32 PHR. CO in these Examples means coplasticizer.

The above data illustrate favorable comparable impact and color performance of interlayer according to the invention with the commercially acceptable Example 20 prior art control.

EXAMPLE 20

This Example measures the edge stability after prolonged exposure to sunlight of interlayers containing the 75/25 DOA/CO plasticizer of Example 19 above in comparison with a DHA control.

0.76 mm thick sheets of plasticized PVB resin were placed between two 15.2 cm x 15.2 cm x 0.23 cm glass plates. The layers were then held in an autoclave for about 7 min at 1.2 MPa, 135°C to laminate the glass and sheet. The laminates were then exposed in Florida at a 45 degree angle facing south and periodically visually observed for signs of edge delamination and compared to a control. Per¬ formance with exposure time was measured by Edge Stability Number (ESN). The ESN for a particular interlayer is based on nine sample laminates con¬ taining such interlayer. ESN is a value obtained by an arbitrary method for calculating edge defects in a laminate which is proportional to the amount of total delamination attributable to the test interlayer for the nine laminate sample of that interlayer. More particularly, it is a mathematical summation of defect length times a weighting factor corresponding to the depth or distance of each defect from the edge of the laminate sample.

After 10.4 months Florida exposure as recited above, laminates containing the Ex. 19 inventive plasticizer formulation had no defects whatsoever and therefore an ESN of 0. The ESN of laminates containing the DHA control had an ESN of 30.

The preceding description is for illustra¬ tion only and is not to be taken in a limited sense. Various modifications and alterations will be readily suggested to persons skilled in the art. It is intended, therefore, that the foregoing be considered as exemplary only and that the scope of the invention be ascertained from the scope of the following claims.

Claims

WE CLAIM

1) A method of improving the effectiveness of dioctyl adipate as a plasticizer for partial poly¬ vinyl butyral resin which comprises incorporating into a mixture of dioctyl phthalate and the resin, an exudation-reducing amount of a composition of i) one or more monoesters of a glycol and a C_lβ to C_?0 un¬ saturated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of said one or more monoesters and castor oil, the ratio of i) to ii) in the mixture of iii) being between about 1:1 to about 5:1.

2) The method of claim 1 wherein the glycol is ethylene glycol or propylene glycol. 3) The method of claim 1 wherein the amount of the composition is adequate to reduce weight loss due to exudation by at least 15% over that occur¬ ring in the absence of the composition.

4) The method of claim 1 wherein the weight ratio of dioctyl adipate to composition is between about 5:1 to 1.9:1.

5) The method of claim 2 wherein the monoester is propylene glycol monoricinoleate

6) The method of any of claims 1,2,3,4 or 5 wherein the composition is the mixture of iii).

7) The method of claim 6 wherein the polyvinyl butyral resin has from 18 to 24 percent unreacted hydroxyl groups, calculated as weight percent of vinyl alcohol. 8) The method of claim 7 wherein the dioctyl adipate is pure di(2-ethyl hexyl) adipate. 9) Polyvinyl butyral resin plasticized with a mixture of a) dioctyl adipate and b) an ex¬ udation-reducing amount of a composition of i) one or more monoesters of a glycol and a C₁₆ to C_2Q unsatu¬ rated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of said one or more monoesters and castor oil, the ratio of one or more monoesters to castor oil in the mixture of iii) being between about 1:1 to about 5:1.

10) The plasticized polyvinyl butyral resin of claim 9 wherein the glycol is ethylene glycol or propylene glycol.

11) The plasticized polyvinyl butyral resin of claim 9 wherein the amount of the composition is adequate to reduce weight loss due to exudation by at least 15% over that occurring in the absence of the composition.

12) The plasticized polyvinyl butyral resin of claim 9 wherein the weight ratio of dioctyl adipate to composition is between about 5:1 to 1.9:1. 13) The plasticized polyvinyl butyral resin of claim 10 wherein the monoester is propylene glycol monoricinoleate.

14) The plasticized polyvinyl butyral resin of any of claims 9, 10, 11 _r 12 or 13 wherein the composition is the mixture of iii).

15) The plasticized polyvinyl butyral resin of claim 14 wherein the polyvinyl butyral resin has from 18 to 24 percent unreacted hydroxyl groups, calculated as weight percent of vinyl alcohol. 16) The plasticized polyvinyl butyral resin of claim 15 wherein the dioctyl adipate is pure di(2-ethyl hexyl) adipate.

17) The plasticized polyvinyl butyral resin of claim 16 wherein the mixture comprises about 65 to 95% dioctyl adipate and 35 to 5% of the compo¬ sition.

18) A sheet of polyvinyl butyral resin plasticized with a mixture of a) dioctyl adipate and b) an exudation-reducing amount of a composition of i) one or more monoesters of a glycol and a C.,, to C_2Q unsaturated fatty acid having a hydroxyl group attached to the acid molecule or ii) castor oil or iii) a mixture of said one or more monoesters and castor oil, the ratio of one or more monoesters to castor oil in the mixture of iii) being between about 1:1 to about 5:1.

19) The sheet of claim 18 wherein the glycol is ethylene glycol or propylene glycol.

20) The sheet of claim 18 wherein the amount of the composition is adequate to reduce weight loss due to exudation by at least 15% over that occurring in the absence of the composition.

21) The sheet of claim 18 wherein the weight ratio of dioctyl adipate to composition is between about 5:1 to 1.9:1. 22) The sheet of claim 19 wherein the the monoester is propylene glycol monoricinoleate.

23) The sheet of any of claims 18, 19, 20, 21 or 22 wherein the composition is the mixture of iii). 24) The sheet of claim 23 wherein the polyvinyl butyral resin has from 18 to 24 percent unreacted hydroxyl groups, calculated as weight percent of vinyl alcohol.

25) The sheet of claim 24 wherein the dioctyl adipate is pure di(2-ethyl hexyl) adipate.

26) The sheet of claim 25 wherein the mixture comprises about 65 to 95% dioctyl adipate and 35 to 5% of the composition.

27) The sheet of claim 26 wherein the mixture comprises 70 to 90% dioctyl adipate and 30 to 10% of the composition.