RU2461429C2 - Method of producing films of parylen and its derivatives - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: method relates to polymer materials, particularly, to making thin polymer films. Proposed method comprises condensation of vapors of parylen and its derivatives on substrate, said vapors being produced by pyrolysis of paracyclophane [2.2] and its derivatives. Said pyrolysis is conducted in inert gas flow at pressure exceeding barometric pressure. Used inert gas relative to monomer represents helium, neon, argon, xenon, krypton carbon dioxide, nitrogen, molecular hydrogen, xylene or toluene.

EFFECT: perfected process.

1 cl, 1 tbl

Description

The invention relates to polymeric materials, specifically to methods for producing thin polymer films. Such materials can be used as protective coatings, films with low dielectric constant, piezoelectric and pyroelectrics, nonlinear optical devices, etc.

In recent years, considerable efforts have been directed towards the development of cost-effective methods for producing various thin-film polymeric materials with useful consumer properties deposited on solid substrates from the gas phase. As a rule, these methods, when implemented, should solve the following general problems.

1. The synthesis or formation of monomer deposited from the gas phase.

2. Transport of monomer from the source of its generation to the substrate.

3. Condensation of the monomer on the substrate with subsequent polymerization and the growth of the polymer film.

A known method for producing thin polymer films (WF Gorham, A new, general synthetic method for the preparation of linear poly-p-xylylenes. J. of Polym. Sci. Part A-1. 1966. V.4. P.3027-3039 ), in which the monomers deposited from the gas phase are obtained by sublimation of a cyclic dimer of paraxylene or substituted with the formation of a gaseous cyclic dimer and its subsequent pyrolysis. As a result of pyrolysis, paraxylene is monomer or substituted, which, upon condensation on a substrate, simultaneously polymerizes to produce poly-paraxylene or substituted. The transport of monomers from the source of their formation to the substrate is carried out by maintaining a low pressure (0.001-0.1 mm Hg) in the condensation zone.

Thus, chemically pure, durable, conformal, low-porous films of various sizes and thicknesses are obtained. It should be emphasized that the films are formed without the use of a solvent, the presence of which can lead to side reactions and affect the quality of the material. Carrying out the process under vacuum leads to the absence of oxygen in the system, which can copolymerize with the monomer, which leads to a significant deterioration in the quality of the coating.

A significant disadvantage in the process of applying a polymer film in a vacuum is the low growth rate when it is formed on a substrate at room temperature. It is impossible to increase the film growth rate by increasing the monomer pressure, since at a monomer pressure of more than 1 Torr, the monomer molecules begin to interact in the gas phase, which leads to the formation of a low molecular weight polymer with poor performance properties. This method is also characterized by a low rate of transport of monomers from the source of their generation to the substrate and a low degree of conversion of the cyclic dimer of paraxylene or its substituted into the final polymer film, which protects the desired object. On the way to the protected substrate (especially if it is significantly removed from the monomer generation source), the monomer prematurely condensates and polymerizes on non-target surfaces. One of the disadvantages of the method is the complexity and high cost of the vacuum installation. In addition, in order to preserve the important properties of a number of coated objects, polymerization often needs to be carried out not in a vacuum, but in the natural environment of the existence of objects (for example, in biotechnology).

Closest to the technical nature of the claimed technical solution is a method for producing thin polymer films by condensation of vapors of paraxylene, obtained by pyrolysis of a cyclic dimer of paraxylene ([2.2] paracyclophan) of its derivatives or mixtures thereof, on a substrate in a stream of He or Ar at a pressure of 1 Torr [US Patent No. 6,165,554, Method for hydrogen atom assisted jet vapor deposition for parylene N and other polymeric thin films, 2000]. According to the specified method receive homogeneous high molecular weight polymer films.

The disadvantage of this method is the use of high power pumping means to ensure high carrier gas flow rates. Another drawback is that the process of condensation and polymerization of the monomer at these pressures requires the control of a large number of technological parameters, since the process proceeds in the viscous mode (the intermediate nature of the process between the kinetic mode (high vacuum), when the film growth is determined by the rate constants of chemical reactions surface of the substrate, and diffusion mode (high pressure), when the growth of the film is determined by the diffusion of the monomer to the surface of the substrate). As a result, the technological parameters of the application largely depend on the design of the installation and its size.

The technical task of the claimed method is to eliminate these drawbacks, which is achieved by the fact that polymer films are obtained by condensation of paraxylene vapor (its derivatives or mixtures thereof) on a substrate in an inert gas stream at a pressure above atmospheric.

The technical result of the invention is to improve the technology for producing films.

Inert gas in the declared solution is considered to be any gas (or its pyrolysis products at the used temperature) that does not chemically react with paraxylene and its derivatives. Such gases are, for example, helium, neon, argon, krypton, xenon, CO ₂ , nitrogen, molecular hydrogen, xylene, toluene, etc.

Vapors of paraxylene and its derivatives are obtained by evaporation and subsequent pyrolysis of [2.2] paracyclophan (PCF) and its derivatives of the general formula:

where X is H, Cl, F;

Y is H, Cl, F, Br, CN, NO ₂ , NH ₂ , N (Al _k ) ₂ .

The difference between the proposed method and the prototype is that the process of producing polymer films occurs in an inert gas stream at a carrier gas pressure above atmospheric. This allows you to abandon the use of vacuum equipment, expands the range of objects on which polymer coatings can be applied (for example, bioobjects). In addition, the growth rate of the films increases, while the consumer properties of polymer films do not deteriorate.

To implement the method, a standard reactor is used [Syrkin V.G. CVD method. Chemical vapor deposition. M .: Science. 2000].

The reactor includes:

1) substrates of various nature, for example, quartz, metal, polymer, on which monomer vapors are condensed. The temperature of the substrate is adjustable;

2) devices for supplying and regulating the flow of carrier gas;

3) high-temperature chambers of evaporation and pyrolysis [2.2] of paracyclophan and its derivatives.

An inert gas (see definition above), which underwent additional catalytic purification from traces of oxygen, was used as a carrier gas. A portion of PCF or its derivatives or mixtures thereof was placed in a sublimation zone. Vapors of PCF or its derivatives or their mixtures from the sublimation zone in an inert gas stream fell into the pyrolysis zone, where they turned into pairs of a non-functional reaction intermediate - p-xylylene or its derivative or mixtures thereof. In the polymerization reactor, paraxylene vapor was adsorbed on a solid support and polymerized to form a polymer coating. The sublimation temperature of PCF or its derivatives or their mixtures was maintained from 120 to 140 ° C. The temperature of the pyrolysis zone was 600 ° C. Polymer coatings were formed on a glass substrate, the temperature of which was varied in the range from -10 to 100 ° C. The flow rate of the carrier gas was maintained from 60 to 200 l / h, which was determined using a rotameter. The pressure of the carrier gas was above one atmosphere and up to 1.5 atmospheres. The minimum pressure of 1.05 atm allows you to abandon the use of pumping facilities. The maximum working pressure of the carrier gas (1.5 atm) is determined by optimizing the flow rate of the carrier gas to maintain the flow rate of the monomer. It is known that it is directly proportional to the flow rate of the carrier gas and inversely proportional to the pressure of the carrier gas. In addition, a significant increase in the flow rate of the carrier gas can lead to a violation of the laminarity of the flow and the contact time of the paracyclophan and its derivatives in the pyrolysis chamber [2.2]. The distance from the monomer source to the substrate was 50-150 cm. During the condensation of paraxyleneylene vapor (its derivatives or mixtures thereof), paraxylene (its derivatives or mixtures thereof) polymerizes on the substrate and a polymer material is formed.

The invention is illustrated by the following examples:

Example 1

[2.2] paracyclophan is charged into the evaporation chamber. The temperature of the substrate in the polymerization reactor is room temperature. The distance from the monomer source to the substrate is 50 cm. The inert carrier gas stream (nitrogen) is turned on, the pressure is 1.05 atm, and the flow rate is 100 l / h. The temperature of the pyrolysis chamber [2.2] of paracyclophan is brought to a temperature of 600 ° C, then the temperature of the evaporation chamber [2.2] of paracyclophan is increased to 140 ° C and the vapor of paraxylene is condensed on the substrate. Condensation time 40 min. The result is a polymer film of polyparaxylene (PPC) with a thickness of 10 μm. The chemical structure of the obtained films corresponds to PPC, which is confirmed by the data of IR and Raman spectroscopy. The IR and Raman spectra of the samples correspond to the SPC spectra obtained by the Gorham method (vacuum conditions). The study of the supramolecular structure of PPC by X-ray analysis showed that the structure of the PPC samples coincides with the structure of the PPC obtained by the Gorkham method. The melting point of PPK samples is 420 ° C, which also corresponds to the melting temperature of PPK obtained by the classical method (under vacuum).

Examples 2-11

Examples 2-11 are shown in the table, they differ in the polymer obtained under various carrier gases and the conditions for the synthesis of the film from the gas phase.

Designations shown in the table:

PPK - polyparaxylylene

CNPPK - Polycyanparaxylylene

2ClPPK - polydichloroparaxylylene

NH ₂ PPK - polyaminoparaxylated

NO ₂ PPK - polynitroparaxylylene

N (CH ₃ ) ₂ PPK - polydimethylaminoparaxylylene

4FPPK - poly-α, α, α`, α`-tetrafluoroparaxylylene

ClPPK - chlorpolyparaxylylene

Claims (2)

1. A method of producing films of polyparaxylylene and its derivatives by condensation on a substrate of vapors of paraxylene and its derivatives obtained by pyrolysis [2.2] of paracyclophan and its derivatives, characterized in that the process is carried out in an inert gas stream at a pressure above atmospheric. 2. The method according to claim 1, characterized in that helium, neon, argon, krypton, xenon, carbon dioxide, nitrogen, molecular hydrogen, xylene or toluene are used as an inert gas with respect to the monomer.