Is immigrants a proper noun

No, the noun 'Immigration' is a common noun, a Word for the action of coming to live permanently in a foreign country; a Word for the immigration of anyone, anywhere.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• US Immigration and Customs Enforcement
• European Union Immigration Services
• Pacific Immigrant Resources Society (non-profit), Vancouver BC Canada
• National Immigration Agency, Ministry of the Interior, Republic of China