HK1170757A - Filled polyimides and methods related thereto - Google Patents

Description

Filled polyimides and methods relating thereto

Technical Field

The present disclosure relates generally to filled polyimides useful in films, fibers, and other articles. The filled polyimides of the present disclosure are useful in electronic device applications, such as coverlay films, due to their favorable dielectric and optical properties.

Background

In the electronics industry, coverlays are commonly used as protective coverlays, such as lead frames for flexible printed circuit boards, electronic components, or integrated circuit packages. The coverlay prevents damage due to scratching, oxidation, and contamination. However, such coverlays suffer from insufficient electrical properties (e.g., dielectric strength), insufficient mechanical strength, or insufficient optical properties, such as undesirable visual inspection that is not aesthetically or safely desirable and that causes damage to the electronic components protected by the coverlay.

Thus, there is a need for coverlays having improved mechanical, electrical, and/or optical properties.

Summary of The Invention

The present disclosure relates to: i. blending polyacrylonitrile into a polyimide precursor to produce a polyimide comprising amorphous carbon domains (hereinafter "filled polyimide"); a process for preparing such filled polyimides; articles made from such filled polyimides.

One aspect of the invention is a composition comprising a blend of polyacrylonitrile and polyimide precursors, wherein:

the polyimide precursor is derived from:

i) at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and

ii) at least 50 mole percent of an aromatic diamine based on the total diamine content in the polyimide precursor;

the polyimide precursor forms a continuous phase in the blend;

the polyacrylonitrile forms domains in the discontinuous phase of the blend;

the weight ratio of polyacrylonitrile to polyimide precursor is about 1: 2 to 1: 50; and is

The polyacrylonitrile has a domain size equal to or less than 2 microns in at least one dimension (and optionally in two dimensions and also optionally in all three dimensions).

Another aspect of the invention is a filled polyimide polymer comprising:

a) a continuous polyimide phase, wherein the polyimide is derived from at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide, and at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide;

b) a dispersed carbon phase comprising carbon domains that are substantially amorphous,

wherein the average carbon domain size is equal to or less than 2 microns; and is

The weight ratio of the dispersed carbon phase to the polyimide phase is about 1: 2 to 1: 50.

Another aspect of the present invention is a filled polyimide polymer obtained by:

a) dispersing a first solution comprising Polyacrylonitrile (PAN) and a first solvent in a second solution comprising a second solvent and a polyimide precursor to form a PAN/polyimide precursor blend, wherein the polyimide precursor forms a continuous phase and the PAN forms a discontinuous phase consisting of PAN domains;

wherein:

the polyimide precursor is derived from at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide precursor;

the weight ratio of PAN to polyimide precursor is about 1: 2 to 1: 50; and is

The average size of the PAN domains is equal to or less than 2 microns in at least one dimension (and optionally in two dimensions and also optionally in all three dimensions); and

b) the PAN/polyimide precursor blend is heated to 300-500 ℃ to convert the PAN domains to substantially amorphous carbon domains and the polyimide precursor to polyimide.

Another aspect of the present invention is a filled polyimide film obtained by:

a) dispersing a first solution comprising Polyacrylonitrile (PAN) and a first solvent in a second solution comprising a second solvent and a polyimide precursor to form a PAN/polyimide precursor blend, wherein the polyimide precursor forms a continuous phase and the PAN forms a discontinuous phase consisting of PAN domains;

wherein:

the polyimide precursor is derived from at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide precursor;

the weight ratio of PAN to polyimide precursor is about 1: 2 to 1: 50;

and the average size of the PAN domain is equal to or less than 2 microns in at least one dimension (and optionally in two dimensions and also optionally in all three dimensions);

b) forming a film from the PAN/polyimide precursor blend; and

c) the PAN/polyimide precursor blend film is heated to 300-500 ℃ to convert the PAN domains to substantially amorphous carbon domains and the polyimide precursor to polyimide.

Another aspect of the invention is a coverlay comprising a filled polyimide film and an adhesive coated on at least one side of the film.

Another aspect of the invention is a filled polyimide fiber obtained by:

a) dispersing a first solution comprising Polyacrylonitrile (PAN) and a first solvent in a second solution comprising a second solvent and a polyimide precursor to form a PAN/polyimide precursor blend, wherein the polyimide precursor forms a continuous phase and the PAN forms a discontinuous phase consisting of PAN domains;

wherein:

the polyimide precursor is derived from at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide precursor; the weight ratio of PAN to polyimide precursor is about 1: 2 to 1: 50; and the average size of the PAN domain is equal to or less than 2 microns in at least one dimension (and optionally in two dimensions and also optionally in all three dimensions);

b) forming a fiber from the PAN/polyimide precursor blend; and

c) the PAN/polyimide precursor blend fiber is heated to 300-.

Brief Description of Drawings

FIG. 1 is a graph of optical density of films made from blends of PAN and PMDA/ODA according to the conditions in example 2 and blends of PAN and PPD/BPDA according to the conditions in example 3 over the visible range of optical density.

Fig. 2 is an SEM cross-section of sample a 3.

Fig. 3 is an SEM cross-section of sample C3.

Detailed Description

The following discussion is merely directed to the preferred embodiments of the present invention, and is not intended to limit the overall scope of the invention. The scope of the invention is only limited by the claims set out at the end of this description.

Definition of

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, process, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such method, process, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, the condition a or B is satisfied in any of the following cases: a is true (or present) and B is spurious (or absent), a is spurious (or absent) and B is true (or present), and both a and B are true (or present).

In addition, "a" or "an" is used to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

As used herein, "dianhydride" is intended to include dianhydrides, precursors or derivatives thereof, which may not be dianhydrides, strictly speaking, but may still react with diamines to form polyamic acids, which may in turn be converted to polyimides.

As used herein, "diamine" is intended to include diamines, precursors or derivatives thereof, which may not be diamines, strictly speaking, but which can still react with a dianhydride to form polyamic acid, which can in turn be converted to polyimide.

"precursor" and "polyamic acid" are used interchangeably and, as used herein, are intended to mean a lower molecular weight polyamic acid solution that can be made by using a stoichiometric excess of diamine to achieve a solution viscosity of about 40-100 poise.

When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

In describing certain polymers, it should be understood that sometimes applicants refer to polymers using the monomers from which they are made or the amounts of the monomers from which they are made. Although such descriptions may not include the specific nomenclature used to describe the final polymer or may not contain terms that define the product by way of a method, any such reference to monomers and amounts should be construed to mean that the polymer is made from those monomers, unless the context indicates or implies otherwise.

Polyamic acid solution

The polyamic acid solution is formed from a diamine component and a dianhydride component that form a polyimide precursor in a suitable solvent. Thus, the polyamic acid solution includes a polyimide precursor and a solvent. In some embodiments, at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content of the polyimide precursor, is present, and at least 50 mole percent of an aromatic diamine, based on the total diamine content of the polyimide precursor. In some embodiments, the aromatic dianhydride is selected from the group consisting of:

pyromellitic dianhydride (PMDA),

3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride (BPDA),

3, 3 ', 4, 4' -Benzophenone Tetracarboxylic Dianhydride (BTDA),

4, 4' -oxydiphthalic anhydride,

3, 3 ', 4, 4' -diphenylsulfone tetracarboxylic dianhydride,

2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane,

Bisphenol A dianhydride, and

mixtures thereof.

In some embodiments, the aromatic diamine is selected from the group consisting of:

3, 4 '-diaminodiphenyl ether (3, 4' -ODA),

1, 3-di- (4-aminophenoxy) benzene (RODA),

4, 4 '-diaminodiphenyl ether (4, 4' -ODA),

1, 4-diaminobenzene (PPD),

1, 3-diaminobenzene (MPD),

2, 2' -bis (trifluoromethyl) benzidine,

4, 4' -diaminobiphenyl,

4, 4' -diaminodiphenyl sulfide,

9, 9' -bis (4-amino) fluorene and

mixtures thereof.

In another embodiment, the diamine is 1, 4-diaminobenzene and the dianhydride is 3, 3 ', 4, 4' -biphenyl tetracarboxylic dianhydride. In another embodiment, the diamine is 4, 4' -diaminodiphenyl ether and the dianhydride is pyromellitic dianhydride. In another embodiment, the diamine is a mixture of 1, 4-diaminobenzene and 1, 3-diaminobenzene and the dianhydride is 3, 3 ', 4, 4' -biphenyl tetracarboxylic dianhydride.

In some embodiments, the polyimide precursor is derived from: 10 to 90 mole% of biphenyl tetracarboxylic dianhydride; 90 to 10 mole% pyromellitic dianhydride; 10 to 90 mole% of 1, 4-diaminobenzene; and 90 to 10 mol% of 4, 4' -diaminodiphenyl ether.

In some embodiments, the diamine component is selected from the group consisting of 1, 4-diaminobenzene and 4, 4' -diaminodiphenyl ether. The dianhydride component is selected from pyromellitic dianhydride and 3, 3 ', 4, 4' -biphenyl tetracarboxylic dianhydride.

In another embodiment, the diamine is a mixture of 1, 4-diaminobenzene PPD and 4, 4 ' -diaminodiphenyl ether ODA and the dianhydride is a mixture of pyromellitic dianhydride PMDA and 3, 3 ', 4, 4 ' -biphenyl tetracarboxylic dianhydride BPDA. In one embodiment, the polyimide is derived from: 10 to 90 mole%, or 30 to 50 mole% of biphenyl tetracarboxylic dianhydride; 90 to 10 mole%, or 70 to 50 mole% pyromellitic dianhydride; 10 to 90 mole%, or 60 to 80 mole%, of 1, 4-diaminobenzene; and 90 to 10 mole%, or 40 to 20 mole% of 4, 4' -diaminodiphenyl ether.

Solvent(s)

A solvent suitable for forming the polyamic acid solution must be capable of dissolving one or both of the polymerization reactant and the polyamic acid polymerization product. The solvent should not substantially react with all of the polymerization reactants and the polyamic acid polymerization product. Suitable solvents include sulfoxide solvents (e.g., dimethyl sulfoxide and diethyl sulfoxide), formamide solvents (e.g., N-dimethylformamide and N, N-diethylformamide), acetamide solvents (e.g., N-dimethylacetamide and N, N-diethylacetamide), pyrrolidone solvents (e.g., N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone), phenol solvents (e.g., phenol, o-, m-or p-cresol, xylenol, halophenols and catechol), hexamethylphosphoramide, tetramethylurea, dimethylsulfone and γ -butyrolactone. These solvents can also be used in combination with aromatic hydrocarbons such as xylene and toluene or with ether-containing solvents such as diglyme, propylene glycol methyl ether, propylene glycol, methyl ether acetate and tetrahydrofuran.

Polyamic acid solution-formation

Polyamic acid solutions are generally prepared by: diamine is dissolved in anhydrous solvent, and dianhydride is slowly added under the conditions of stirring and temperature control in an inert atmosphere. In one embodiment, the diamine is present as a 5 to 15 weight percent solution in the solvent, and the diamine and dianhydride are generally used in about equimolar amounts.

There may be a variety of embodiments formed, for example: (a) a method in which a diamine component and a dianhydride component are mixed together in advance and then the mixture is added to a solvent in portions while stirring, (b) a method in which a solvent is added to a mixture of the diamine and the dianhydride component while stirring, (c) a method in which a diamine is separately dissolved in a solvent and then a dianhydride is added thereto, (d) a method in which a dianhydride component is separately dissolved in a solvent and then an amine component is added thereto, (e) a method in which a diamine component and a dianhydride component are separately dissolved in a solvent and then these solutions are mixed in a reactor, (f) a method in which polyamic acid having an excess of the amine component and another polyamic acid having an excess of the dianhydride component are preliminarily formed and then reacted with each other in a reactor, particularly a non-random or block copolymer is formed in this manner, and (g) a method in which a specified proportion of the amine component is first reacted with the dianhydride component and then the remaining diamine component is reacted, or vice versa, (h) a method in which the components are added partially or completely in any order to some or all of the solvents, and some or all of any of the components may be added in solution to some or all of the solvents, and (i) a method in which one dianhydride component is first reacted with one of the diamine components to obtain a first polyamic acid, and then the other dianhydride component is reacted with the other amine component to obtain a second polyamic acid, and then the polyamic acids are mixed in any of a variety of ways before forming the film or fiber.

The dianhydride and diamine components are typically mixed in a molar ratio of aromatic dianhydride component to aromatic diamine component of from 0.90 to 1.10. The molecular weight can be adjusted by adjusting the molar ratio of the dianhydride and diamine components.

In one embodiment, the polyamic acid solution is dissolved in the organic solvent at a concentration of about 5, 10, or 12 wt% to about 12, 15, 20, 25, 27, 30 wt%.

If a filled polyimide is used as the film, the polyamic acid solution can be mixed with a conversion compound comprising: (i) one or more dehydrating agents, such as aliphatic anhydrides (e.g., acetic anhydride) and aromatic anhydrides; and (ii) one or more catalysts, such as aliphatic tertiary amines (e.g., triethylamine), aromatic tertiary amines (e.g., dimethylaniline), and heterocyclic tertiary amines (e.g., pyridine, picoline, and isoquinoline). The anhydride dehydrating agent is generally used in a molar excess over the amic acid groups in the copolyamic acid. Acetic anhydride is generally used in an amount of about 2.0 to 3.0 moles per equivalent of copolyamide acid. Generally, a substantial amount of tertiary amine catalyst is used.

Polyacrylonitrile

For use in the present invention, the Polyacrylonitrile (PAN) polymer must be dissolved in a solvent such as Dimethylformamide (DMF), N-Dimethylacetamide (DMAC) or N-methylpyrrolidone (NMP). The PAN solution may be formed by heating PAN in a selected solvent. A solution of 5-25 wt% PAN is used to form a PAN dispersion in the polyimide precursor.

In some embodiments, the polyacrylonitrile is a homopolymer. In another embodiment, polyacrylonitrile is a copolymer containing up to 10 mole% of methyl acrylate, vinyl acetate, methacrylic acid, itaconic acid, or mixtures thereof. Polyacrylonitrile is commercially available from, for example, Sigma-Aldrich chemical company (St. Louis, Mo., USA).

Blend formation

One aspect of the invention is a blend of polyacrylonitrile and polyimide precursors, where the polyacrylonitrile forms a discontinuous dispersed phase in the polyimide precursor continuous phase. The phase may comprise a solvent in addition to the polymer and/or precursor.

The blend is formed by mixing a PAN solution and a polyimide precursor solution. For best results, high shear is used, for example using a rotating revolving stirrer. The blend comprises PAN and polyimide in a weight ratio of 1: 2 to 1: 50, or 1: 5 to 1: 50, or 1: 10 to 1: 50.

Typically, the average domain size of the PAN phase is 0.1 to 2 microns, preferably 0.25 to 0.75 microns, as determined by SEM.

Formation of polymer blend films

The blend can be cast or applied onto a support such as a glass, metal or polymeric substrate or an endless belt or drum to obtain a film. The film containing the solvent is then converted to a self-supporting film by heating in air or nitrogen at 80 to 200 ℃. In some embodiments, the film is then separated from the support, oriented by, for example, tentering and continued heating (curing) in nitrogen at 300-500 ℃ to provide a filled polyimide film in which the polyimide precursor has been converted to polyimide and the PAN has been substantially converted to amorphous carbon. In some embodiments, a curing temperature of 400 ℃ is employed. In other embodiments, the film remains on the support during the curing process.

After curing, the filled polyimide film is highly colored, ranging in color from brown to black. Deeper colors are obtained with higher PAN to polyimide precursor ratios and/or by more intense heating (i.e., higher temperatures and/or longer times) during the curing step. Thus, the color intensity can be fine tuned by adjusting the temperature, the curing time, or both.

Typically, the cured film has gloss, but a matte finish can be achieved by adding a matting agent at any stage of the process prior to casting or by treating the surface of the cured film. Typical matting agents include amorphous silicas such as precipitated silicas, fumed silicas, diatomaceous earths and silica gels. Other matting agents include organic polymer particles (e.g., polyimide powder), inorganic particles, metal stearates, and nanoparticles.

In some embodiments, the desired optical density (opacity) (e.g., no wires in the flex circuit are visible) is greater than or equal to 2. An optical density of 2 is intended to mean 1X 10^-2Or 1% ofLight is transmitted through the film.

Since the blend contains solvents that must be removed during the drying and converting steps, the cast film must generally be bound during drying to avoid undesirable shrinkage. In continuous production, the film may be held at the edges, for example in a tenter frame, using tenter clips or pins for binding. Alternatively, the film may be stretched up to 200% from its original dimensions. In film manufacture, stretching can be in the machine direction or the transverse direction or both. If desired, a tether can also be provided to allow a limited degree of contraction.

The film can be dried at a high temperature for a short time and imidization can be initiated in the same step to convert the polyimide precursor into polyimide. Generally, thin films require less heat and time than thick films.

The film thickness can be adjusted according to the intended use or end-use specifications of the film. The film thickness is generally preferably in the range of 2, 3, 5, 7, 8, 10, 12, 15, 20, or 25 microns to about 25, 30, 35, 40, 45, 50, 60, 80, 100, 125, 150, 175, 200, 300, 400, or 500 microns. Preferably about 8 to about 125 microns thick.

The uniform dispersion of the segregated carbon domains not only reduces conductivity, but also tends to produce uniform color intensity. In some embodiments, the average particle size of the PAN-derived carbon is between (and optionally includes) any two of the following sizes: 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, and 2.0 microns. The film thickness can be tailored to the specific application.

Formation of polymer blend fibers

Filled polyimide fibers can also be made from a blend of polyacrylonitrile and polyimide precursors. The fibers may be spun from the blend and then heated to convert the polyimide precursor to a continuous polyimide phase and the polyacrylonitrile to a discontinuous carbon phase. A high temperature imidization/carbonization step may be performed on the fibers immediately after spinning. Alternatively, a yarn, fabric or article made from the fibers may be heated to an appropriate temperature.

Watch protective layer

The filled polyimide films described herein can be used as coverlay films for flexible printed circuit boards, electronic components, or integrated circuit package lead frames.

Adhesive agent

In one embodiment, the coverlay film includes a filled polyimide film and an adhesive layer for holding the coverlay film in place after application. Examples of adhesives that may be used to form the adhesive layer include thermoplastic polyimide resins, epoxy resins, phenolic resins, melamine resins, acrylic resins, cyanate ester resins, and combinations thereof. In some embodiments, the adhesive is a polyimide resin capable of flowing and bonding at temperatures below the decomposition temperature of the polyimide. In one embodiment, the adhesive is a polyimide thermoplastic resin, optionally further comprising a thermosetting adhesive such as an epoxy resin and/or a phenolic resin. In the case of the adhesive having a thermoplastic component and a thermosetting component, the content of the thermosetting resin in the adhesive layer is generally in the range of 5 to 400 parts by weight, preferably 50 to 200 parts by weight, per 100 parts by weight of the resin component which is not a thermosetting resin.

In one embodiment, the adhesive is comprised of an epoxy resin and a hardener and optionally further comprises additional components such as elastomer reinforcing agents, cure accelerators, fillers and flame retardants.

In some embodiments, the adhesive is an epoxy selected from the group consisting of: bisphenol a epoxy resin; bisphenol F epoxy resin; bisphenol S epoxy resin; a novolac type epoxy resin; cresol novolac type epoxy resins; biphenyl epoxy resin; biphenyl aralkyl epoxy resins; an aralkyl epoxy resin; dicyclopentadiene epoxy resin; a multifunctional epoxy resin; naphthalene epoxy resin; a phosphorus-containing epoxy resin; rubber modified epoxy resins, and mixtures thereof.

In some embodiments, the epoxy adhesive comprises a hardener. Suitable hardeners include phenolic compounds selected from: a phenol-aldehyde phenol resin; an aralkyl phenol resin; a biphenyl aralkyl phenol resin; a multifunctional phenol resin; a nitrogen-containing phenol resin; a dicyclopentadiene phenol resin; and a phosphorus-containing phenol resin.

In another embodiment, the hardener is an aromatic diamine compound selected from the group consisting of: diaminobiphenyl compounds such as 4, 4 ' -diaminobiphenyl and 4, 4 ' -diamino-2, 2 ' -dimethylbiphenyl; diaminodiphenylalkane compounds such as 4, 4 '-diaminodiphenylmethane and 4, 4' -diaminodiphenylethane; diaminodiphenyl ether compounds such as 4, 4' -diaminodiphenyl ether and bis (4-amino-3-ethylphenyl) ether; diaminodiphenyl sulfide compounds such as 4, 4' -diaminodiphenyl sulfide and bis (4-amino-3-propylphenyl) sulfide; diamino diphenyl sulfone compounds such as 4, 4' -diamino diphenyl sulfone and bis (4-amino-3-isopropylphenyl) sulfone; and phenylenediamine. In one embodiment, the hardener is an amine compound selected from the group consisting of: guanidines, such as Dicyandiamide (DICY); and aliphatic diamines such as ethylenediamine and diethylenediamine.

In the following examples, all parts and percentages are by weight unless otherwise indicated.

Examples

The materials, methods, and examples herein are illustrative only and are not intended to be limiting unless specifically indicated. Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, suitable methods and materials are described herein.

All materials were obtained from Sigma-Aldrich Chemical Company (St. Louis, MO, USA) unless otherwise specified.

The surface gloss was measured using a Horiba Handy gloss meter (model: IG-310). The visible optical density was measured using X-rite339 from X-rite (Grand Rapids, MI, USA).

The PAN-PI blend was mixed using a rotating and revolving mixer from THINKY (model: ARE-310).

The dielectric constant and the tangent loss were measured by ASTM D-2520: a sample having a thickness of 100mm X100 mm was measured, and then the thin film was put into a rectangular waveguide cavity. The dielectric constant was measured by the frequency change of the first six odd mode resonances (2.2GHz, 3.4GHz, 5.0GHz, 6.8GHz, 8.6GHz and 10.4 GHz). The tangent loss is measured by comparing the change in quality factor at each measured resonance. The Damoskos model 003 test fixture was used in conjunction with an Anritsu 37000 series vector network Analyzer.

Volume and surface resistivity-ASTM-D-247: a Hewlett Packard 16008A resistivity cell was used in conjunction with a Hewlett Packard 4329A high resistance meter.

Example 1 PAN in Polymer H

Polyacrylonitrile (PAN, 0.92g) was dissolved in 9.2g Dimethylformamide (DMF) over 4 hours at 85 ℃ in a glass jar. The resulting 10 wt% PAN solution was continuously stirred on a hot plate using a magnetic stirrer.

Polyamic acid was prepared from pyromellitic dianhydride (PMDA) and 4, 4' -diaminodiphenyl ether (ODA) in a molar ratio of 0.98: 1 in DMAC, having 17 weight percent solids and a viscosity of about 40-100 poise using standard procedures. To this solution was added a freshly prepared 6 wt% PMDA solution of DMAC in small portions to gradually increase the molecular weight of the polyamic acid. The final viscosity was about 477 poise and was used to prepare blends of PAN and PMDA/ODA precursors at 10 and 37 wt%.

The polymer solution (39.9g of polyamic acid and 1.082g of PAN) was mixed at room temperature for 1 minute at a rate of 2000RPM using a rotating and revolving agitator. The polymer blend film was coated on a 7 "x 7" glass plate using a 10 mil BYK-Gardner rod type applicator and air dried on a 90 ℃ hot plate for 45 minutes. The film was then cured at 450 ℃ for 20 minutes under nitrogen. The film was black in color.

Example 2 PAN in PMDA/ODA

Polyacrylonitrile (0.5069g) was dissolved in dimethylformamide (9.5g) in a glass jar over 4 hours at 90 ℃. The resulting 5.1 wt.% polymer solution was continuously stirred on a hot plate using a magnetic stirrer. This solution was used as a stock solution for the preparation of several PAN and PMDA/ODA precursor blends as described in table 1.

Polyamic acid was prepared from PMDA and ODA in a 0.98: 1 molar ratio in DMAC, having 20.6 wt.% solids and a viscosity of about 40-100 poise using standard procedures. To this polyamic acid solution, a freshly prepared 6 wt% PMDA solution of DMAC was added in small portions to gradually increase the molecular weight of the polymer. The final viscosity was about 1500 poise and 186.1 grams of polyamic acid solution was used as a stock solution for preparing various PAN and PMDA/ODA precursor blends as described in table 1.

Table 1: preparation of polyimide/polyacrylonitrile films from PMDA/ODA polymers

Each blend was mixed twice at room temperature using a rotating orbital agitator at a rate of 2000RPM for 30 seconds. Films made from various PAN and PMDA/ODA blends were coated on 7 "x 7" glass plates using a 10 mil BYK-Gardner rod type applicator. The films were allowed to dry in air on a 90 ℃ hot plate for 45 minutes and cured under nitrogen as described in table 1.

The film color changed from the natural color of the polyimide to dark brown, and a darker color could be obtained using more than 2 wt% PAN or increasing the curing temperature and/or curing time. The gloss of the cured film decreased with decreasing weight percent PAN in the PMDA/ODA.

The visible optical density increased with increasing weight percent PAN in the PMDA/ODA, with example 2 having the highest density of 2.6. The visible density difference of 0.43 between comparative example C and comparative example D indicates that curing the film at elevated temperature and for extended time yields a more highly colored film.

Example 2 showed no significant change in dielectric constant, tangent loss, and volume resistivity compared to the polyimide film prepared by the standard method. The average dielectric constant ranged from 3.6 at 2.17GHz and dropped slightly to 3.5 at 10.4 GHz. The average tangent loss ranged from 0.016 at 2.17GHz to 0.022 at 10.4 GHz. Volume resistivity greater than 10¹⁵(Ω-cm)。

Example 3 PAN in BPDA/PPD Polymer

Polyacrylonitrile (8.1g) was dissolved in dimethylformamide (40.55g) in a glass jar at 85 ℃ over 3.5 hours. The resulting 19.95 wt% PAN solution was continuously stirred on a hot plate using a magnetic stirrer. This solution was used as a stock solution for preparing various PAN and BPDA/PPD precursor blends as described in table 2.

Polyamic acid (48.8g) having 17 wt.% solids and a viscosity of about 40-100 poise was prepared from 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride (BPDA) and 1, 4-diaminobenzene (PPD) in a 0.98: 1 molar ratio in DMAC using standard procedures. To this polyamic acid solution, a freshly prepared 6 wt% PMDA solution of DMAC was added in small portions to gradually increase the molecular weight of the polymer. The final viscosity was about 650 poise and was used as a stock solution for preparing various PAN and BPDA/PPD precursor blends as described in table 2.

Table 2: preparation of polyimide/polyacrylonitrile films from BPDA/PPD polymers

Each blend was mixed twice at room temperature using a rotating orbital agitator at a rate of 2000RPM for 30 seconds. Films made from various PAN and BPDA/PPD blends were coated on 7 "x 7" glass plates using a 10 mil BYK-Gardner rod type applicator. The films were air dried on a 90 ℃ hot plate for 45 minutes and cured under nitrogen as described in table 2. The film was black, flexible and completely opaque.

Scanning Electron Microscopy (SEM) was used to map the cross section of the cured film perpendicular to the coating direction. The SEM cross-section of sample a3 shown in fig. 2 shows a uniform distribution of carbon domains with a width of less than about 1 micron. In addition, many voids near or surrounding the carbon domains are visible within the SEM cross-section. The void width is less than the carbon domain width. The SEM cross section of sample C3 shown in fig. 3 coincided with a higher weight percent PAN in the polyimide, as more carbon domains were visible in the cross section. There are also many voids near or around the carbon domains. The carbon domains in sample C3 are larger than the domains in sample A3. Some of the domains in sample C3 appear as aggregates of domains. Interestingly, the domains formed in samples a3 or C3 did not penetrate or form networks, which is consistent with the observation that the dielectric constant, the tangent loss and the volume resistivity remained unchanged in the presence of PAN in polyimide.

FIG. 1 is a graph of optical density of films in the visible optical density range, the films made from blends of PAN and PMDA/ODA according to the conditions in example 2 and blends of PAN and BPDA/PPD according to the conditions in example 3.

Claims (15)

1. A composition comprising a blend of polyacrylonitrile and a polyimide precursor, wherein:

the polyimide precursor is derived from:

a. at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and

b. at least 50 mole percent of an aromatic diamine based on the total diamine content in the polyimide precursor;

the polyimide precursor forms a continuous phase in the blend;

the polyacrylonitrile forms domains in the discontinuous phase of the blend;

the weight ratio of polyacrylonitrile to polyimide precursor is about 1: 2 to 1: 50; and is

The polyacrylonitrile has a domain size equal to or less than 2 microns in at least one dimension.

2. The composition of claim 1, wherein

a. The aromatic dianhydride is selected from:

pyromellitic dianhydride,

3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride,

3, 3 ', 4, 4' -benzophenone tetracarboxylic dianhydride,

4, 4' -oxydiphthalic anhydride,

3, 3 ', 4, 4' -diphenylsulfone tetracarboxylic dianhydride,

2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane,

Bisphenol A dianhydride, and

mixtures thereof; and is

b. The aromatic diamine is selected from:

3, 4' -diaminodiphenyl ether,

1, 3-di- (4-aminophenoxy) benzene,

4, 4' -diaminodiphenyl ether,

1, 4-diaminobenzene,

1, 3-diaminobenzene,

2, 2' -bis (trifluoromethyl) benzidine,

4, 4' -diaminobiphenyl,

4, 4' -diaminodiphenyl sulfide,

9, 9' -bis (4-amino) fluorene and

mixtures thereof.

3. The composition of claim 1, wherein the diamine is 1, 4-diaminobenzene and the dianhydride is 3, 3 ', 4, 4' -biphenyl tetracarboxylic dianhydride.

4. The composition of claim 1, wherein the diamine is 4, 4' -diaminodiphenyl ether and the dianhydride is pyromellitic dianhydride.

5. The composition of claim 1, wherein the polyimide precursor is derived from: 10 to 90 mole% of biphenyl tetracarboxylic dianhydride; 90 to 10 mole% pyromellitic dianhydride; 10 to 90 mole% of 1, 4-diaminobenzene; and 90 to 10 mol% of 4, 4' -diaminodiphenyl ether.

6. The composition of claim 1, wherein the diamine is a mixture of 1, 4-diaminobenzene and 1, 3-diaminobenzene and the dianhydride is 3, 3 ', 4, 4' -biphenyl tetracarboxylic dianhydride.

7. A filled polyimide polymer, said polymer comprising:

a) a continuous polyimide phase, wherein the polyimide is derived from

i. At least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide, and

at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide; and

b) a dispersed carbon phase comprising carbon domains that are substantially amorphous,

wherein the average carbon domain size is equal to or less than 2 microns in at least one dimension; and is

The weight ratio of the dispersed carbon phase to the polyimide phase is from 1: 10 to 1: 50.

8. A filled polyimide polymer, said polymer obtained by:

a) dispersing a first solution comprising Polyacrylonitrile (PAN) and a first solvent in a second solution comprising a second solvent and a polyimide precursor to form a PAN/polyimide precursor blend, wherein the polyimide precursor forms a continuous phase and the PAN forms a discontinuous phase consisting of PAN domains;

wherein:

the polyimide precursor is derived from at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide precursor; and is

The weight ratio of PAN to polyimide precursor is about 1: 2 to 1: 50; and is

An average size of the PAN domain is equal to or less than 2 microns in at least one dimension;

and

b) the PAN/polyimide precursor blend is heated to 300-500 ℃ to convert the PAN domains to substantially amorphous carbon domains and the polyimide precursor to polyimide.

9. A filled polyimide film, said film obtained by:

a) dispersing a first solution comprising Polyacrylonitrile (PAN) and a first solvent in a second solution comprising a second solvent and a polyimide precursor to form a PAN/polyimide precursor blend, wherein the polyimide precursor forms a continuous phase and the PAN forms a discontinuous phase consisting of PAN domains; wherein

The polyimide precursor is derived from at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide precursor;

the weight ratio of PAN to polyimide precursor is about 1: 2 to 1: 50; and is

An average size of the PAN domain is equal to or less than 2 microns in at least one dimension;

b) forming a film from the PAN/polyimide precursor blend; and

c) the PAN/polyimide precursor blend film is heated to 300-500 ℃ to convert the PAN domains to substantially amorphous carbon domains and the polyimide precursor to polyimide.

10. The filled polyimide film of claim 9 wherein the film has a thickness of 2 to 500 microns.

11. A coverlay comprising the filled polyimide film of claim 9 and an adhesive coated on at least one side of the film.

12. The coverlay of claim 11, wherein the binder is selected from the group consisting of thermoplastic polyimide resins, epoxy resins, phenolic resins, melamine resins, acrylic resins, cyanate ester resins, and combinations thereof.

13. The coverlay of claim 11, wherein the adhesive is a polyimide thermoplastic resin, optionally further comprising a thermosetting adhesive selected from the group consisting of epoxy resins and phenolic resins.

14. The coverlay of claim 11, wherein the adhesive is an epoxy selected from the group consisting of: bisphenol a epoxy resin; bisphenol F epoxy resin; bisphenol S epoxy resin; a novolac type epoxy resin; cresol novolac type epoxy resins; biphenyl epoxy resin; biphenyl aralkyl epoxy resins; an aralkyl epoxy resin; dicyclopentadiene epoxy resin; a multifunctional epoxy resin; naphthalene epoxy resin; a phosphorus-containing epoxy resin; rubber modified epoxy resins, and mixtures thereof.

15. A filled polyimide fiber, said fiber obtained by:

a) dispersing a first solution comprising Polyacrylonitrile (PAN) and a first solvent in a second solution comprising a second solvent and a polyimide precursor to form a PAN/polyimide precursor blend, wherein the polyimide precursor forms a continuous phase and the PAN forms a discontinuous phase consisting of PAN domains;

wherein:

the polyimide precursor is derived from at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content in the polyimide precursor, and at least 50 mole percent of an aromatic diamine, based on the total diamine content in the polyimide precursor;

the weight ratio of PAN to polyimide precursor is 1: 2 to 1: 50; and is

An average size of the PAN domain is equal to or less than 2 microns in at least one dimension;

b) forming a fiber from the PAN/polyimide precursor blend; and

c) the PAN/polyimide precursor blend fiber is heated to 300-.