KR920003081B1 - Interpolymers of ethylene and unsaturated carboxylic acids - Google Patents

Abstract

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Description

Process for preparing interpolymer of ethylene and unsaturated carboxylic acid

FIG. 1 presents a visual understanding of the concept of the present invention in a curve showing the ratio of weight average molecular weight (MWw) / number average molecular weight (MWn) under synthetic conditions.

The present invention relates to a process for preparing interpolymers using ethylene and carboxylic acid comonomers.

Interpolymers of ethylene and unsaturated carboxylic acids such as acrylic acid and methacrylic acid are well known. The interpolymers of the present invention are free-formed in agitated reactors under steady state or in a high pressure and elevated temperature stirred reactor under steady state as opposed to polymers and block polymers or graft copolymers prepared in a batch reaction without stirring or in batch reactions. And such interpolymers prepared using radical initiators.

Interpolymerization processes of ethylene and unsaturated carboxylic acids in steady state reactions at high pressure, high temperature in the presence of free radical initiators in stirred reactors are described in Canadian Patent No. 655,298 (and its corresponding US Pat. No. 4,351,931), US Pat. No. 3,239,370 3,520,861, 3,658,741, 3,884,857, 3,988,509, 4,248,990 and 4,252,924.

U.S. Patent No. 3,239,370 discloses ethylene random copolymerization with unsaturated carboxylic acids (e.g. acrylic acid) using peroxide initiators in stirred autoclaves operating at 16,000 psi and 210 ° C, and the resulting copolymers are particularly useful as coatings for nonmetallic substrates. It is said.

U.S. Patent No. 3,520,861 describes a substantially homogeneous, compositionally consistent copolymer of ethylene / unsaturated acid prepared in a continuous manner using free radical initiators (e.g. peroxides) in agitated autoclaves operated at high pressures and elevated temperatures. Doing. The polymerization temperature is in the range of about 120 ° to about 300 ° C, preferably about 150 ° to about 250 ° C, and the polymerization pressure is at least 1000 atmospheres, preferably about 1000 to 3000 atmospheres, in particular 1100 to 1900 atmospheres.

Canadian Patent 655,298 and its corresponding U.S. Patent No. 4,351,931 describe a uniform, compositionally consistent random copolymer of ethylene and an unsaturated carboxylic acid (e.g. acrylic acid), having a melt index of 0.01 to 30 g. It contains at least about 90% by weight of ethylene, which is 10 minutes. This copolymer continuously supplied the monomer using a free radical initiator in a good stirred reactor operated at 90 to 280 ° C. or higher at a pressure of 1000 atm and a ratio of ethylene / acid to 10,000 / 1 to 50/1 by weight. And a reaction mixture is removed to maintain a constant reaction environment.

U.S. Patent No. 3,658,741 describes homogeneous copolymers of ethylene and unsaturated carboxylic acids prepared using vortex stirring at temperatures of 100 to 300 ° C. and pressures of 100 to 1000 atmospheres in the presence of chain transfer agents, free radical catalysts, where the reaction is It occurs in the medium phase and describes that very small molar weight copolymers are produced.

U.S. Patent Nos. 3,884,857 and 3,988,509 describe a process for preparing copolymers such as ethylene / acrylic acid copolymers by continuous high pressure, free radical polymerization at 100 to 250 ° C and 1000 to 2500 atmospheres.

US Pat. No. 4,248,990 describes copolymers, such as ethylene / acrylic acid copolymers, which are nonrandom in terms of random copolymers from Canadian, 655,298 and US Pat. No. 3,520,861. This non-randomity is obtained by operating a steady-state, high pressure, stirred reactor at a pressure of 0 to about 500 psi or higher and a temperature of 0 to 15 ° C. or higher, wherein the concentration of a given copolymer in the reaction mixture and the given acid content of the copolymer It is indicated that the reaction mixture of the single phase must be maintained at the monomer content.

US Pat. No. 4,252,924 uses non-random by using a single-phase reaction mixture in a series of stirred autoclaves in two or more constant environments, each of which maintains the temperature of each subsequent autoclave above 30 ° C. above the entire autoclave. Described are methods for preparing copolymers, such as ethylene / acrylic acid copolymers.

In the ordinary case, those skilled in the art do not seek to consume more than the energy (temperature and / or pressure) needed to obtain a given product unless the profit can be guaranteed beyond the excess cost. In the present invention, it is possible to pursue profits beyond expectations by using energy (temperature and pressure) more than the amount generally required for the preparation of the interpolymer of ethylene.

In a random interpolymer of ethylene and olefinically unsaturated organic comonomers prepared in a good stirred autoclave that is continuously operated at about constant temperature and pressure at nearly constant conditions in the presence of free radicals, surprisingly and unexpectedly given in the polymerization mixture So that the comonomer concentration and the polymer concentration can approach, reach and / or exceed individual molecular weight distribution (MMD) boundaries, i.e., the synthetic conditions where the ratio of weight average molecular weight (MWw) / number average molecular weight (MWn) is maximum. It has been found that substantial and useful improvements are made by maintaining the synthesis conditions with sufficiently high temperatures and pressures above the phase boundaries present between phases and single phases.

It can be seen from FIG. 1 that the ratio of the weight average molecular weight to the number average molecular weight increases as the synthetic conditions increase to exceed the phase boundary and almost beyond the conditions under which single phase manipulation occurs.

That is, the MWD expands until it finally reaches and exceeds the boundary of the molecular weight distribution (MWD). According to FIG. 1, an increase in the ratio of MWw / MWn can be achieved by using a film made from copolymers prepared above the temperature, the pressure, the synthetic conditions reaching the phase boundary and the nonrandom range described in US Pat. No. 4,248,990 and This can be achieved by improving the quality of the product. A more beneficial effect is seen beyond the MWD boundary, where the MWD decreases and the MWw / MWn ratio decreases.

The inventive concept is widely applicable to the interpolymers of ethylene (where ethylene constitutes the majority of the monomer mixture) and olefinically unsaturated organic comonomers, and in particular, the present invention relates to acrylates, methacrylates, vinyls as comonomers. Applicable to esters and olefinically unsaturated carboxylic acids. In particular, the present invention is most applicable and preferably used for preparing polymers which interpolymerize ethylene with acrylic acid or methacrylic acid. Preference is given to using acrylic acid and methacrylic acid as comonomers.

It is also an object of the present invention to produce improved homogeneous random ethylene copolymers, in particular improved copolymers of ethylene and carboxylic acid comonomers. The present invention is to provide an ethylene copolymer which is particularly suitable for bonding, coating and / or packaging and extrusion resins. This object is particularly useful for copolymers of ethylene with 0.1 to 35% by weight of α, β-ethylenically unsaturated carboxylic acids (e.g. acrylic acid and methacrylic acid) having a melt index in the range of 0.01 to 5000 g / 10 minutes (ASTM D1238E). Is achieved by manufacturing.

“Homogenization, random” means that almost all copolymer molecules have almost the same chemical composition, even if they have different molecular weights, and the ratio of the weight percent of adjacent acids to the total weight of carboxylic acids in the copolymer is less than 0.44 (determined according to US Pat. No. 4,248,990). As).

The copolymers of the present invention have toughness, flexibility and chemical resistance with excellent transparency, increased heat seal strength, improved heat adhesive strength, excellent extrusion coating and reduced microgel concentration. One surprising feature of the copolymers of the present invention is the excellent transparency obtained at relatively low comonomer concentrations (ie <10% by weight).

Copolymers of the present invention have transparency at such low concentrations that can usually only be achieved by additional steps of high concentrations of acid or acid-salt neutralization (see US Pat. Nos. 3,264,272, 4,248,990, and 4,351,931). Thus, these copolymers are used for applications such as flexible packaging, which have the added advantage of excellent processability as well as special draw-down, ease of handling, adhesion and printability (without corona or other forms of pretreatment). It is extremely useful as a blown film having high transparency.

In addition, the interpolymers of the present invention can be readily prepared to have a molecular weight distribution suitable for coatings that exhibits improved draw ratio, adhesion and seal strength (determined by gel permeation chromatography, which may require esterification pretreatment). .

Conventional ethylene / carboxylic acid comonomers commonly known in the art have the optical properties of poor blown films and therefore are not widely used for packaging. Thus, acid-salt neutralization methods for the production of ionomers known in the art are often used to impart complete transparency to the acid copolymer. However, the preparation of ionomers reduces the amount of adhesion by neutralizing carboxylic acids or acid groups that impart adhesion. Typically, ionomer products should be pretreated to restore proper adhesion to blown film converters, coaters and viscous units. Another drawback of known production routes for transparent adhesive film grades or application grade products is that it is more difficult to rheologically produce ionomers on conventional polyethylene extrusion equipment (i.e. ionomers require high amperage and have to cool the extruder). Disadvantageously, it is moisture sensitive.

Commercially poor copolymers are characterized by a relatively wide molecular weight distribution and / or inadequate homogeneity. Pieski and Sashihara (US Pat. No. 4,248,990) indicate that the homogeneity of the copolymers is due to single phase synthesis. Thus, in order to prepare a homogeneous (but non-random) copolymer of US Pat. No. 4,248,990, the position of the phase boundary (ie, the transition point from two phases to a single phase) must be identified, and the reaction zone, i.e. the transition point is from 0 to about 500 psi. It should be maintained at a steady state at the reactor pressure of above and the reactor temperature of 0 to about 15 ℃ or more.

The "monophase" product with the improved homogeneity described in US Pat. No. 4,248,990 has proven to have a lower microgel or grain concentration than the "2nd phase" product. However, these single phase products are still produced in synthetic conditions very close to their respective phase boundaries and therefore still contain a significant amount of sharpness. These single phase products also exhibit a wider molecular weight distribution (than the two phase products), resulting in poor transparency, and therefore acid-salt neutralization is required to increase the transparency required for various packaging applications. The wide molecular weight distribution of these “monolithic” products, not offset by improved homogeneity, also reduces the maximum draw ratio of the film, filament or coating as compared to the biphasic product.

At the synthesis temperatures and pressures in the above ranges specified by Pieski and Sashihara, the resulting single-phase product is a random (as opposed to non-random) product with a relatively low percentage of adjacent acid to weight percent total carboxylic acid. Such single phase products (such as those produced at a specific range of synthesis conditions just above the phase boundaries) have a broader molecular weight distribution as the reactor temperature and pressure gradually increase.

In FIG. 1, which shows the MWw / MWn ratio for the synthesis conditions, the curve is represented by a curve reaching the peak indicated by the MWD boundary.

The lower end point of the curve corresponding to the lower end point of the synthesis conditions represents the phase boundary between the two phases and the single phase. The two-phase part of the curve is indicated by (1). The non-random single phase portion described by Pieskie and Sashihara (US Pat. No. 4,248,990), denoted by (2), is an air produced at process conditions at which phase boundaries appear, i.e., at least 0 to 500 psi and at least 0 to 15 ° C. The relative position of the curve with respect to coalescing is shown. All products produced under synthetic conditions above the perimeter are single phase products. The curved portion denoted by (3) indicates the relative position between the non-random single phase portion 2 and the MWD boundary located in the random single phase portion. After the MWD boundary, there is a random single-phase curve portion, denoted by (4), which represents a product with a ratio that is almost in the same range as (2) and (3), but was not expected in this portion. An improved product is obtained. The curve in part (5) shows products with almost the same ratios obtainable in two phase conditions, but this is a significant improvement over the two phase products. Referring to FIG. 1, the improved products found on both sides of the MWD boundary, i.e. on the process conditions that provide the non-random product, are within the scope of the present invention, in particular the products at positions (4) and (5) of the ratio curve. to be.

According to the present invention, homogeneous random single-phase ethylene copolymers with markedly improved transparency, heat seal strength, heat adhesion strength and molecular weight distribution similar to biphasic products can be prepared at or above the phase boundaries and described in US Pat. No. 4,248,990. Easily manufactured above random range. It has now been found that transition boundaries exist in a broad to narrow molecular weight distribution, similar to the phase boundary. Unlike phase boundaries, the MWD boundaries are not identified by dramatic changes in the required initiator or by significant changes in the reactor stirrer motor amperage, which are well known to those skilled in the art. Do not.

However, this position can be conveniently identified at a given comonomer concentration by finding discontinuities in the molecular weight distribution at a constant melt index of the product, and the concentration of comonomer as a synthetic condition is determined by the molecular weight distribution (MDW) boundary (Figure 1). It can change in the way it passes. Before reaching this molecular weight distribution (MWD) boundary, the random single phase product has a broader molecular weight distribution than the two phase product and the nonrandom single phase product to be compared. However, by reaching the MWD boundary, random single-phase products surprisingly gain homogeneity, which offsets their broad molecular weight distribution and imparts significantly improved transparency, heat seal strength and lock ratio. As the synthesis conditions are further and / or gradually increased beyond the MWD boundary, the individual molecular weight distributions become relatively narrow.

In other words, the ratio of MWw / MWn is reduced. Thus, by using suitable synthetic conditions, it is possible to conveniently prepare a single phase product having a molecular weight distribution corresponding to that of the two phase product, and as a result, a good product can be obtained. Random single phase products prepared under synthetic conditions approaching, reaching, or exceeding the MWD boundary are distinct from known known nonrandom single phase products and random two phase products, and have the same comonomer concentration and polymer in the polymerization mixture. At concentrations, the product of the present invention has a ratio of weight average molecular weight to number average molecular weight defined as follows.

Where MWw is the weight average molecular weight, MWn is the number average molecular weight and C ₁ is the comonomer weight fraction versus the given comonomer

는 주어진 공단량체 형태의 MWD경계에서의 MWn에 대한 MWw의 비이며, C₂는 주어진 공단량체 형태에 대해 공단량체 중량분률 대

곡선의 기울기이며, C₃는 약 0.75 내지 1.0, 바람직하게는 약 0.85 내지 약 1.0 범위의 수치이고, C₄는 약 1.0 내지 약 0.1범위의 수치이며 이때, C₃는 단일상 비랜덤 번위와 MWD경계 사이에서 생성물을 제조하는 공정 조건에서 사용되고, C₄는 MWD경계이상에서 생성물을 제조하는 공정 조건에서 사용된다. MWD경계에서, C₃및 C₄는 모두 동일하게 1이다.Is the intercept of the curve, where

Is the ratio of MWw to MWn in the MWD boundary of a given comonomer form, and C ₂ is the comonomer weight fraction versus the given comonomer form

Is the slope of the curve, C ₃ is a value in the range of about 0.75 to 1.0, preferably about 0.85 to about 1.0, and C ₄ is a value in the range of about 1.0 to about 0.1, where C ₃ is the single phase nonrandom number and the MWD It is used at the process conditions for producing the product between the boundaries, and C ₄ is used at the process conditions for producing the product above the MWD boundary. In the MWD boundary, C ₃ and C ₄ are all equal to 1.

Since the quality of the product is closely related to the molecular weight distribution (e.g. narrow molecular weight distribution is necessary to obtain a copolymer with good transparency, a relatively wide MWD is usually required for excellent extrusion coating). It is possible to produce a wide distinct distribution in the melt index and to produce products suitable for a wide range of films, coatings, moldings and laminates.

The exact location of the MWD boundary depends on the concentration of the comonomer and several other variables, but such testing demonstrates that the location is just above the corresponding phase boundary for a given comonomer concentration. For example, the MWD boundary occurs at a phase boundary, at least 2000 psi, at least 15 ° when an ethylene / acrylic acid copolymer containing 9% by weight acrylic acid is produced.

In addition to the ability to have the desired molecular weight distribution or improved transparency and coating properties, according to the invention, below the MWD boundary, at the boundary, the single-phase products produced above are, for example, US Pat. No. 4,248,990 Not only is there less sharpness than the non-random single phase products produced in the arc, but they also have fewer microgels or sharps than the comparable biphasic products. In fact, products with no sharpness can easily be obtained above the corresponding MWD boundaries or boundaries. This reduction in microgels or sharpness is also important for aesthetics. Too much sharpness may result in inadequate heat seal and heat adhesion strength, which degrades adhesion and promotes delamination. It is also an object of the present invention to open the heat seal strength and heat adhesive strength of such single phase products.

The copolymer of the present invention can be conveniently prepared in a reactor at a pressure of about 18,000 to 50,000 psi and a temperature of about 150 ° to 350 ° C. as long as the phase separation conditions are noticeably exceeded. Preferred reactors are continuous autoclaves with L / D ratios of 1: 1 to about 16: 1. One or more reaction zones may be present by installing a conventional baffling system in the reactor, the reactor may be present in one or more other reactors in series, and the reactor may be as described by British Patent No. 1,096,945. It may have more than one comonomer entry point. Thus, when more than one reaction zone is used, the reactor (s) can be adjusted to create a constant environment in the middle and / or intermediate zones or manipulated so that there is a difference in environment between and / or within the reaction zones and / or reactors. You may.

The products of the present invention may be prepared with or without carriers and / or initiators for hydrocarbons and / or comonomer (s) as solvents or terogens. These products are also useful as base resins for the preparation of ionic copolymers known in the art as ionomers, from which further improvements in transparency, chemical resistance and thermal adhesion strength are easily obtained.

Gels that often characterize ethylene / carboxylic acid interpolymers can exist in many different shapes and sizes beyond the original. For example, microgels or grains (i.e. very small and fine gels) appear according to the invention when operated at or very close to the individual phase boundaries, and large gels (i.e. Gels larger than 25 microns) typically appear as a result of thermal oxidation / degradation, but in practice microgels or sharps can seed these larger gels.

In the present invention, the following gel grades are used.

The following examples illustrate aspects of the invention but do not limit the invention to the described embodiments.

Example 1 (for comparison)

A 1.5 mil blown film was prepared from an ethylene / acrylic acid copolymer containing 6.5 weight percent acrylic acid and having a melt index of 2.5 g / 10 min (ASTM D 1238E). The copolymer is prepared at its individual phase boundary of at least about 0 to 500 psi and at least 0 to 15 ° C. and the film has excessive microgels or sharps, Gardner transparency of 12% transmission, 20 ° film glossiness of 25% reflection, 5.5% dispersion. It has a film haze of light, a heat seal strength of 3.2ιbs / inch width at a sealing bar temperature of 310 ° F and a heat adhesion strength of 150g / inch at a 300 ° F sealing bar temperature.

Example 2

In contrast, 6.5% by weight acrylic acid copolymer having the same melt index is prepared at a corresponding phase of at least about 3500 to 4500 psi and at least about 16 to 18 ° C. The resulting blown film has 47% Gardner transparency, 45% 20 ° gloss, 3.2% film haze, negligible microgels or sharps, 4.9ιbs / inch heat seal strength at 310 ° F and 200 g / inch thermal adhesion strength at 300 ° F. All film samples are made of 1.5 mil films on an NMR 20/1, L / D extruder equipped with air rings, mandrel annular dies, and take-off units. All manufactured have a blowing rate of 2.25: 1 and a melting point of 204 ° C.

Data for samples of the above examples and additional ethylene / acrylic acid copolymers are shown in the table below. Examples 1,5,8,11 and 15 are examples of prior art used in the preparation of non-random copolymers at phase boundary pressures and temperatures above, i.e., pressures above 0 to 500 psi and temperatures above 0 to 15 [deg.] C. The examples illustrate various aspects of the present invention, all of which are produced at temperatures above the phase boundary temperature.

TABLE 1

TABLE 2

blown film manufacturing conditions: 204 ° C, 2.25BUR, 1.5mils (thickness), NRM extruder

TABLE 3

TABLE 4

d Black Klauson extrusion coater (3-1 / 2 "extruder, 30/1 L / D); Melting point 550 ℉, screw speed 85RPM, void 6

* Psi below the MWD boundary.

TABLE 5

d Black Klauson extrusion coater (3-1 / 2 "extruder, 30/1 L / D); Melting point 550 ℉, screw speed 85RPM, air gap 6 inches

* Psi below the MWD boundary.

Claims (13)

Under a constant environment and steady-state conditions, a small amount of ethylene and a small amount of ethylene in a good stirred reactor in which the monomer is fed into the reactor in the presence of a free-radical initiator as a single-phase reaction mixture and the reaction mixture is In the process for producing homogeneous random interpolymers of olefinically unsaturated organic monomers, the synthesis of elevated temperatures and elevated pressures beyond the phase boundary between two-phase and single-phase operation to approach, reach or exceed molecular weight distribution boundaries. Conditions [where the molecular weight distribution boundary is the maximum ratio of the weight average molecular weight / number average molecular weight that can be obtained in single phase operation, and the elevated temperature and the elevated pressure are the synthetic conditions required at the phase boundary for the mixture of the given ethylene and comonomer, respectively. At least 2000 psi and at least 15 ° C.]. The method of claim 1 wherein the olefinically unsaturated organic monomer comprises at least one acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate and vinyl ester. The method of claim 1 wherein the olefinically unsaturated organic monomer comprises acrylic acid or methacrylic acid. The method of claim 1 wherein the olefinically unsaturated organic monomer is acrylic acid. The method of claim 1 wherein the olefinically unsaturated organic monomer is methacrylic acid. The process of claim 1 wherein the prepared interpolymer comprises 65 to 99 weight percent ethylene units in the polymer chain. The process of claim 1 wherein the prepared interpolymer comprises 88 to 99% by weight of ethylene units in the polymer chain. The method of claim 1, wherein the synthesis conditions include elevated temperatures in the range of 150 to 350 ° C. and elevated pressures in the range of 18,000 to 50,000 psi, wherein the pressure and temperature are at least a minimum amount of temperature and a pressure of at least 2000 psi to obtain a single phase reaction mixture. , Wherein the elevated temperature and elevated pressure are temperatures and pressures above and above the temperature and pressure reaching the molecular weight distribution boundary of the thus prepared interpolymer. A small amount of one or more (weight) copolymerizable with ethylene carried out in a good stirred autoclave reactor operated in steady state at steady state conditions using free radical polymerization initiators at constant temperature, pressure and flow rate. In a method for producing a homogeneous, random interpolymer with an olefinically unsaturated comonomer, the temperature and pressure conditions required for operation at the phase boundary are at least 500 psi above the temperature at the phase boundary and the pressure at the phase boundary, respectively. How to use pressure. 10. The method of claim 9, wherein the olefinically unsaturated comonomer which can be co-condensed is an unsaturated carboxylic acid. The method of claim 9, wherein the olefinically unsaturated comonomer that can be copolymerized is acrylic acid or methacrylic acid. 10. The method of claim 9, wherein the olefinically unsaturated comonomer that can be copolymerized is acrylic acid. 10. The method of claim 9, wherein the interpolymer comprises at least 65 wt% ethylene groups.

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